diff --git a/ganttzk/src/main/java/org/zkoss/ganttz/util/MutableTreeModel.java b/ganttzk/src/main/java/org/zkoss/ganttz/util/MutableTreeModel.java
index fec55eedf..976d6eeac 100644
--- a/ganttzk/src/main/java/org/zkoss/ganttz/util/MutableTreeModel.java
+++ b/ganttzk/src/main/java/org/zkoss/ganttz/util/MutableTreeModel.java
@@ -324,4 +324,8 @@ public class MutableTreeModel<T> extends AbstractTreeModel {
         return getChildCount(getRoot()) == 0;
     }
 
+    public boolean hasChildren(T node) {
+        return getChildCount(node) > 0;
+    }
+
 }
diff --git a/navalplanner-business/src/main/resources/org/navalplanner/business/materials/entities/Materials.hbm.xml b/navalplanner-business/src/main/resources/org/navalplanner/business/materials/entities/Materials.hbm.xml
index 5270c0461..330997c8e 100644
--- a/navalplanner-business/src/main/resources/org/navalplanner/business/materials/entities/Materials.hbm.xml
+++ b/navalplanner-business/src/main/resources/org/navalplanner/business/materials/entities/Materials.hbm.xml
@@ -11,7 +11,7 @@
     </id>
     <version name="version" access="property" type="long" />
 
-    <property name="code" unique="true"/>
+    <property name="code" unique="true" not-null="true"/>
 
     <property name="description"/>
 
diff --git a/navalplanner-webapp/src/main/java/org/navalplanner/web/materials/IMaterialsModel.java b/navalplanner-webapp/src/main/java/org/navalplanner/web/materials/IMaterialsModel.java
index 66dbc9286..941f80b40 100644
--- a/navalplanner-webapp/src/main/java/org/navalplanner/web/materials/IMaterialsModel.java
+++ b/navalplanner-webapp/src/main/java/org/navalplanner/web/materials/IMaterialsModel.java
@@ -36,12 +36,14 @@ public interface IMaterialsModel {
 
     void addMaterialCategory(MaterialCategory parent, MaterialCategory child) throws ValidationException;
 
+    void addMaterialToMaterialCategory(MaterialCategory materialCategory);
+
+    void confirmSave() throws ValidationException;
+
     MutableTreeModel<MaterialCategory> getMaterialCategories();
 
+    List<Material> getMaterials(MaterialCategory materialCategory);
+
     void removeMaterialCategory(MaterialCategory materialCategory);
 
-	void addMaterialToMaterialCategory(MaterialCategory materialCategory);
-
-	List<Material> getMaterials();
-
 }
diff --git a/navalplanner-webapp/src/main/java/org/navalplanner/web/materials/MaterialsController.java b/navalplanner-webapp/src/main/java/org/navalplanner/web/materials/MaterialsController.java
index 471bc6d2f..ce25f4e48 100644
--- a/navalplanner-webapp/src/main/java/org/navalplanner/web/materials/MaterialsController.java
+++ b/navalplanner-webapp/src/main/java/org/navalplanner/web/materials/MaterialsController.java
@@ -22,6 +22,7 @@ package org.navalplanner.web.materials;
 
 import static org.navalplanner.web.I18nHelper._;
 
+import java.util.ArrayList;
 import java.util.Collection;
 import java.util.List;
 
@@ -32,6 +33,7 @@ import org.navalplanner.business.materials.entities.Material;
 import org.navalplanner.business.materials.entities.MaterialCategory;
 import org.navalplanner.web.common.IMessagesForUser;
 import org.navalplanner.web.common.Level;
+import org.navalplanner.web.common.MessagesForUser;
 import org.navalplanner.web.common.Util;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.zkoss.zk.ui.Component;
@@ -43,6 +45,7 @@ import org.zkoss.zk.ui.util.GenericForwardComposer;
 import org.zkoss.zul.Button;
 import org.zkoss.zul.Grid;
 import org.zkoss.zul.Messagebox;
+import org.zkoss.zul.SimpleListModel;
 import org.zkoss.zul.Textbox;
 import org.zkoss.zul.Tree;
 import org.zkoss.zul.TreeModel;
@@ -68,7 +71,7 @@ public class MaterialsController extends
 
     private Tree categoriesTree;
 
-    private Grid materials;
+    private Grid gridMaterials;
 
     private Textbox txtCategory;
 
@@ -81,6 +84,7 @@ public class MaterialsController extends
     public void doAfterCompose(Component comp) throws Exception {
         super.doAfterCompose(comp);
         comp.setVariable("materialsController", this, true);
+        messagesForUser = new MessagesForUser(messagesContainer);
     }
 
     public TreeModel getMaterialCategories() {
@@ -233,11 +237,52 @@ public class MaterialsController extends
         }
         final MaterialCategory materialCategory = (MaterialCategory) treeitem.getValue();
         materialsModel.addMaterialToMaterialCategory(materialCategory);
-        Util.reloadBindings(materials);
+        Util.reloadBindings(gridMaterials);
+    }
+
+    public void saveAndExit() {
+        save();
+        messagesForUser.showMessage(Level.INFO, _("Materials saved"));
+    }
+
+    private void save() {
+        validate();
+        try {
+            materialsModel.confirmSave();
+        } catch (ValidationException e) {
+            messagesForUser.showInvalidValues(e);
+        }
+    }
+
+    private void validate() {
+        ConstraintChecker.
+    }
+
+    public void saveAndContinue() {
+
+    }
+
+    public void cancel() {
+
+    }
+
+    public void refreshMaterials() {
+        final List<Material> materials = getMaterials();
+        gridMaterials.setModel(new SimpleListModel(materials));
+        Util.reloadBindings(gridMaterials);
     }
 
     public List<Material> getMaterials() {
-        return materialsModel.getMaterials();
+        return getMaterials(categoriesTree.getSelectedItem());
+    }
+
+    private List<Material> getMaterials(Treeitem treeitem) {
+        final List<Material> result = new ArrayList<Material>();
+        if (treeitem != null) {
+            final MaterialCategory materialCategory = (MaterialCategory) treeitem.getValue();
+            result.addAll(materialsModel.getMaterials(materialCategory));
+        }
+        return result;
     }
 
 }
diff --git a/navalplanner-webapp/src/main/java/org/navalplanner/web/materials/MaterialsModel.java b/navalplanner-webapp/src/main/java/org/navalplanner/web/materials/MaterialsModel.java
index 0d875b3ce..817e1bfb0 100644
--- a/navalplanner-webapp/src/main/java/org/navalplanner/web/materials/MaterialsModel.java
+++ b/navalplanner-webapp/src/main/java/org/navalplanner/web/materials/MaterialsModel.java
@@ -7,6 +7,7 @@ import java.util.List;
 import java.util.Set;
 
 import org.apache.commons.lang.Validate;
+import org.hibernate.Hibernate;
 import org.hibernate.validator.InvalidValue;
 import org.navalplanner.business.common.exceptions.ValidationException;
 import org.navalplanner.business.materials.daos.IMaterialCategoryDAO;
@@ -32,31 +33,7 @@ public class MaterialsModel implements IMaterialsModel {
 
     MutableTreeModel<MaterialCategory> materialCategories = MutableTreeModel.create(MaterialCategory.class);
 
-    List<Material> materials = new ArrayList<Material>();
-
-    private void initializeMaterialCategories() {
-        final List<MaterialCategory> categories = categoryDAO.getAllRootMaterialCategories();
-        for (MaterialCategory materialCategory: categories) {
-            materialCategories.addToRoot(materialCategory);
-            addCategories(materialCategory, materialCategory.getSubcategories());
-        }
-    }
-
-    @SuppressWarnings("unchecked")
-    private void initializeMaterials() {
-        materials = new ArrayList(materialDAO.getAll());
-    }
-
-    private void addCategories(MaterialCategory materialCategory, Set<MaterialCategory> categories) {
-        for (MaterialCategory category: categories) {
-            materialCategories.add(materialCategory, category);
-            final Set<MaterialCategory> subcategories = category.getSubcategories();
-            if (subcategories != null) {
-                addCategories(category, subcategories);
-            }
-        }
-    }
-
+    @Override
     @Transactional(readOnly=true)
     public MutableTreeModel<MaterialCategory> getMaterialCategories() {
         if (materialCategories.isEmpty()) {
@@ -65,13 +42,38 @@ public class MaterialsModel implements IMaterialsModel {
         return materialCategories;
     }
 
+    private void initializeMaterialCategories() {
+        final List<MaterialCategory> categories = categoryDAO.getAllRootMaterialCategories();
+        for (MaterialCategory materialCategory: categories) {
+            initializeMaterials(materialCategory.getMaterials());
+            materialCategories.addToRoot(materialCategory);
+            addCategories(materialCategory, materialCategory.getSubcategories());
+        }
+    }
+
+    private void initializeMaterials(Set<Material> materials) {
+        for (Material each: materials) {
+            each.getDescription();
+        }
+    }
+
+    private void addCategories(MaterialCategory materialCategory, Set<MaterialCategory> categories) {
+        for (MaterialCategory category: categories) {
+            initializeMaterials(category.getMaterials());
+            materialCategories.add(materialCategory, category);
+            final Set<MaterialCategory> subcategories = category.getSubcategories();
+            if (subcategories != null) {
+                addCategories(category, subcategories);
+            }
+        }
+    }
+
     @Override
     @Transactional(readOnly=true)
-    public List<Material> getMaterials() {
-        if (materials.isEmpty()) {
-            initializeMaterials();
-        }
-        return materials;
+    public List<Material> getMaterials(MaterialCategory materialCategory) {
+        List<Material> result = new ArrayList<Material>();
+        result.addAll(materialCategory.getMaterials());
+        return result;
     }
 
     @Override
@@ -115,7 +117,30 @@ public class MaterialsModel implements IMaterialsModel {
     public void addMaterialToMaterialCategory(MaterialCategory materialCategory) {
         Material material = Material.create("");
         material.setCategory(materialCategory);
-        materials.add(material);
+        materialCategory.addMaterial(material);
+    }
+
+    @Override
+    @Transactional
+    public void confirmSave() throws ValidationException {
+        List<MaterialCategory> categories = new ArrayList<MaterialCategory>();
+        asList(materialCategories.getRoot(), categories);
+        for (MaterialCategory each: categories) {
+            categoryDAO.save(each);
+        }
+    }
+
+    private void asList(MaterialCategory root, List<MaterialCategory> result) {
+        List<MaterialCategory> list = new ArrayList<MaterialCategory>();
+        for (int i = 0; i < materialCategories.getChildCount(root); i++) {
+            final MaterialCategory materialCategory = materialCategories.getChild(root, i);
+            list.add(materialCategory);
+            result.add(materialCategory);
+        }
+
+        for (MaterialCategory each: list) {
+            asList(each, result);
+        }
     }
 
 }
diff --git a/navalplanner-webapp/src/main/webapp/materials/materials.zul b/navalplanner-webapp/src/main/webapp/materials/materials.zul
index 7b009630a..81db15d58 100644
--- a/navalplanner-webapp/src/main/webapp/materials/materials.zul
+++ b/navalplanner-webapp/src/main/webapp/materials/materials.zul
@@ -1,21 +1,21 @@
 <!--
-  This file is part of ###PROJECT_NAME###
+    This file is part of ###PROJECT_NAME###
 
-  Copyright (C) 2009 Fundación para o Fomento da Calidade Industrial e
-                     Desenvolvemento Tecnolóxico de Galicia
+    Copyright (C) 2009 Fundación para o Fomento da Calidade Industrial e
+    Desenvolvemento Tecnolóxico de Galicia
 
-  This program is free software: you can redistribute it and/or modify
-  it under the terms of the GNU Affero General Public License as published by
-  the Free Software Foundation, either version 3 of the License, or
-  (at your option) any later version.
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU Affero General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
 
-  This program is distributed in the hope that it will be useful,
-  but WITHOUT ANY WARRANTY; without even the implied warranty of
-  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-  GNU Affero General Public License for more details.
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU Affero General Public License for more details.
 
-  You should have received a copy of the GNU Affero General Public License
-  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+    You should have received a copy of the GNU Affero General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
 -->
 
 <?page  id="labelTypesList"?>
@@ -29,57 +29,93 @@
 
 <zk>
     <window self="@{define(content)}"
-        apply="org.navalplanner.web.materials.MaterialsController" >
-
-        <hbox>
-
+        apply="org.navalplanner.web.materials.MaterialsController">
         <vbox id="messagesContainer" />
+        <tabbox>
+            <tabs>
+                <tab label="${i18n:_('Materials')}"></tab>
+            </tabs>
+            <tabpanels>
+                <tabpanel>
+                    <hbox>
+                        <!-- Categories  -->
+                        <vbox>
+                            <panel title="${i18n:_('Categories')}"
+                                border="normal">
+                                <panelchildren>
+                                    <textbox id="txtCategory"
+                                        style="margin-bottom: 4px;" />
+                                    <button label="${i18n:_('Add')}"
+                                        onClick="materialsController.addMaterialCategory()" />
+                                    <tree id="categoriesTree"
+                                        width="280px" rows="10" vflex="true" multiple="true"
+                                        model="@{materialsController.materialCategories}"
+                                        treeitemRenderer="@{materialsController.materialCategoryRenderer}"
+                                        onSelect="materialsController.refreshMaterials()">
+                                        <treecols>
+                                            <treecol label="Name" />
+                                            <treecol label="" />
+                                        </treecols>
+                                    </tree>
+                                </panelchildren>
+                            </panel>
+                        </vbox>
 
-        <vbox>
-            <panel title="${i18n:_('Categories')}" border="normal">
-                <panelchildren>
-                    <textbox id="txtCategory" style="margin-bottom: 4px;" />
-                    <button label="${i18n:_('Add')}" onClick="materialsController.addMaterialCategory()"/>
-                    <tree id="categoriesTree" width="280px" rows="10"
-                        vflex="true" multiple="true"
-                        model="@{materialsController.materialCategories}"
-                        treeitemRenderer="@{materialsController.materialCategoryRenderer}">
-                        <treecols>
-                            <treecol label="Name" />
-                            <treecol label="" />
-                        </treecols>
-                    </tree>
-                </panelchildren>
-            </panel>
-        </vbox>
+                        <!-- Materials -->
+                        <vbox>
+                            <panel title="${i18n:_('Materials')}"
+                                border="normal">
+                                <panelchildren>
+                                    <button label="${i18n:_('Add')}"
+                                        onClick="materialsController.addMaterialToMaterialCategory(categoriesTree.selectedItem)" />
+                                    <grid id="gridMaterials"
+                                        fixedLayout="true"
+                                        model="@{materialsController.materials}">
+                                        <columns>
+                                            <column
+                                                label="${i18n:_('Code')}" />
+                                            <column
+                                                label="${i18n:_('Description')}" />
+                                            <column
+                                                label="${i18n:_('Unit price')}" />
+                                            <column
+                                                label="${i18n:_('Unit type')}" />
+                                            <column
+                                                label="${i18n:_('Disabled')}" />
+                                        </columns>
+                                        <rows>
+                                            <row
+                                                self="@{each='material'}" value="@{material}">
+                                                <textbox
+                                                    value="@{material.code}" constraint="no empty:${i18n:_('cannot be null or empty')}" />
+                                                <textbox
+                                                    value="@{material.description}" />
+                                                <intbox
+                                                    value="@{material.defaultUnitPrice}" constraint="no empty:${i18n:_('cannot be null or empty')}" />
+                                                <textbox
+                                                    value="@{material.unitType}" constraint="no empty:${i18n:_('cannot be null or empty')}" />
+                                                <checkbox
+                                                    checked="@{material.disabled}" />
+                                            </row>
+                                        </rows>
+                                    </grid>
 
-        <vbox>
-            <panel title="${i18n:_('Materials')}" border="normal">
-                <panelchildren>
-                    <button label="${i18n:_('Add')}" onClick="materialsController.addMaterialToMaterialCategory(categoriesTree.selectedItem)"/>
-                    <grid id="materials" model="@{materialsController.materials}">
-                        <columns>
-                            <column label="${i18n:_('Code')}"/>
-                            <column label="${i18n:_('Description')}"/>
-                            <column label="${i18n:_('Unit price')}"/>
-                            <column label="${i18n:_('Unit type')}"/>
-                            <column label="${i18n:_('Disabled')}"/>
-                        </columns>
-                        <rows>
-                            <row self="@{each='material'}" value="@{material}">
-                                <textbox value="@{material.code}" />
-                                <textbox value="@{material.description}" />
-                                <textbox value="@{material.defaultUnitPrice}" />
-                                <textbox value="@{material.unitType}" />
-                                <checkbox checked="@{material.disabled}" />
-                            </row>
-                        </rows>
-                    </grid>
-                </panelchildren>
-            </panel>
-        </vbox>
+                                </panelchildren>
+                            </panel>
+                        </vbox>
 
-        </hbox>
+                    </hbox>
+                </tabpanel>
+            </tabpanels>
+        </tabbox>
+
+        <button onClick="materialsController.saveAndExit()"
+            label="${i18n:_('Save')}" />
+        <button onClick="materialsController.saveAndContinue()"
+            label="${i18n:_('Save &amp; Continue')}" />
+        <button onClick="materialsController.cancel()"
+            label="${i18n:_('Cancel')}" />
 
     </window>
+
 </zk>