diff --git a/Filtration/Models/ItemFilterBlockGroup.cs b/Filtration/Models/ItemFilterBlockGroup.cs
index 218123e..851542f 100644
--- a/Filtration/Models/ItemFilterBlockGroup.cs
+++ b/Filtration/Models/ItemFilterBlockGroup.cs
@@ -1,14 +1,21 @@
-using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using System.ComponentModel;
+using System.Linq;
+using System.Runtime.CompilerServices;
+using Filtration.Annotations;
 
 namespace Filtration.Models
 {
-    internal class ItemFilterBlockGroup
+    internal class ItemFilterBlockGroup : INotifyPropertyChanged
     {
+        private bool? _isChecked;
+        private bool _reentrancyCheck;
+
         public ItemFilterBlockGroup(string groupName, ItemFilterBlockGroup parent)
         {
             GroupName = groupName;
             ParentGroup = parent;
-            ChildGroups = new List<ItemFilterBlockGroup>();
+            ChildGroups = new ObservableCollection<ItemFilterBlockGroup>();
         }
 
         public override string ToString()
@@ -32,6 +39,79 @@ namespace Filtration.Models
 
         public string GroupName { get; private set; }
         public ItemFilterBlockGroup ParentGroup { get; private set; }
-        public List<ItemFilterBlockGroup> ChildGroups { get; private set; } 
+        public ObservableCollection<ItemFilterBlockGroup> ChildGroups { get; private set; }
+
+        public bool? IsChecked
+        {
+            get
+            {
+                return _isChecked;
+            }
+            set
+            {
+                if (_isChecked != value)
+                {
+                    if (_reentrancyCheck)
+                    {
+                        return;
+                    }
+                    _reentrancyCheck = true;
+                    _isChecked = value;
+                    UpdateCheckState();
+                    OnPropertyChanged();
+                    _reentrancyCheck = false;
+                }
+            }
+        }
+
+        private void UpdateCheckState()
+        {
+            // update all children:
+            if (ChildGroups.Count != 0)
+            {
+                UpdateChildrenCheckState();
+            }
+
+            // update parent item
+            if (ParentGroup != null)
+            {
+                var parentIsChecked = ParentGroup.DetermineCheckState();
+                ParentGroup.IsChecked = parentIsChecked;
+            }
+        }
+
+        private void UpdateChildrenCheckState()
+        {
+            foreach (var childGroup in ChildGroups.Where(c => IsChecked != null))
+            {
+                childGroup.IsChecked = IsChecked;
+            }
+        }
+
+        private bool? DetermineCheckState()
+        {
+            var allChildrenChecked = ChildGroups.Count(x => x.IsChecked == true) == ChildGroups.Count;
+            if (allChildrenChecked)
+            {
+                return true;
+            }
+
+            var allChildrenUnchecked = ChildGroups.Count(x => x.IsChecked == false) == ChildGroups.Count;
+            if (allChildrenUnchecked)
+            {
+                return false;
+            }
+
+            return null;
+        }
+
+        public event PropertyChangedEventHandler PropertyChanged;
+
+        [NotifyPropertyChangedInvocator]
+        protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
+        {
+            var handler = PropertyChanged;
+            if (handler != null) handler(this, new PropertyChangedEventArgs(propertyName));
+        }
     }
 }
diff --git a/Filtration/Views/AvalonDock/AvalonDockWorkspaceView.xaml b/Filtration/Views/AvalonDock/AvalonDockWorkspaceView.xaml
index bc00bb8..895f80c 100644
--- a/Filtration/Views/AvalonDock/AvalonDockWorkspaceView.xaml
+++ b/Filtration/Views/AvalonDock/AvalonDockWorkspaceView.xaml
@@ -10,7 +10,7 @@
              xmlns:xcad="http://schemas.xceed.com/wpf/xaml/avalondock"
              xmlns:converters="clr-namespace:Filtration.Converters"
              mc:Ignorable="d" 
-             d:DataContext="{d:DesignInstance Type=viewModels:AvalonDockWorkspaceViewModel}"
+             d:DataContext="{d:DesignInstance d:Type=viewModels:AvalonDockWorkspaceViewModel}"
              d:DesignHeight="300" d:DesignWidth="300">
     <UserControl.Resources>
         <BooleanToVisibilityConverter x:Key="BooleanToVisibilityConverter" />
diff --git a/Filtration/Views/AvalonDock/AvalonDockWorkspaceView.xaml.cs b/Filtration/Views/AvalonDock/AvalonDockWorkspaceView.xaml.cs
new file mode 100644
index 0000000..b76a69f
--- /dev/null
+++ b/Filtration/Views/AvalonDock/AvalonDockWorkspaceView.xaml.cs
@@ -0,0 +1,10 @@
+namespace Filtration.Views.AvalonDock
+{
+    public partial class AvalonDockWorkspaceView
+    {
+        public AvalonDockWorkspaceView()
+        {
+            InitializeComponent();
+        }
+    }
+}
diff --git a/Filtration/Views/ToolPanes/BlockGroupBrowserView.xaml b/Filtration/Views/ToolPanes/BlockGroupBrowserView.xaml
index 1085365..807cc16 100644
--- a/Filtration/Views/ToolPanes/BlockGroupBrowserView.xaml
+++ b/Filtration/Views/ToolPanes/BlockGroupBrowserView.xaml
@@ -16,7 +16,7 @@
             <TreeView.Resources>
                 <HierarchicalDataTemplate DataType="{x:Type models:ItemFilterBlockGroup}" ItemsSource="{Binding ChildGroups}">
                     <WrapPanel>
-                        <CheckBox IsThreeState="True" />
+                        <CheckBox IsThreeState="True" IsChecked="{Binding IsChecked}" Click="BlockGroupCheckBox_Clicked"  />
                         <TextBlock Text="{Binding GroupName}" />
                     </WrapPanel>
                 </HierarchicalDataTemplate>