diff --git a/Gtk/Perspex.Gtk/WindowImpl.cs b/Gtk/Perspex.Gtk/WindowImpl.cs
index 502eaaa36a..c736b9d946 100644
--- a/Gtk/Perspex.Gtk/WindowImpl.cs
+++ b/Gtk/Perspex.Gtk/WindowImpl.cs
@@ -7,6 +7,7 @@
 namespace Perspex.Gtk
 {
     using System;
+    using System.Threading.Tasks;
     using Perspex.Controls;
     using Perspex.Input.Raw;
     using Perspex.Platform;
@@ -79,6 +80,16 @@ namespace Perspex.Gtk
             this.Title = title;
         }
 
+        public IDisposable ShowDialog()
+        {
+            throw new NotImplementedException();
+        }
+
+        void ITopLevelImpl.Activate()
+        {
+            this.Activate();
+        }
+
         protected override bool OnButtonPressEvent(Gdk.EventButton evnt)
         {
             var e = new RawMouseEventArgs(
diff --git a/Perspex.Controls/Platform/ITopLevelImpl.cs b/Perspex.Controls/Platform/ITopLevelImpl.cs
index 96c642d158..2802dad621 100644
--- a/Perspex.Controls/Platform/ITopLevelImpl.cs
+++ b/Perspex.Controls/Platform/ITopLevelImpl.cs
@@ -29,6 +29,8 @@ namespace Perspex.Platform
 
         Action<Size> Resized { get; set; }
 
+        void Activate();
+
         void Invalidate(Rect rect);
 
         void SetOwner(TopLevel owner);
diff --git a/Perspex.Controls/Platform/IWindowImpl.cs b/Perspex.Controls/Platform/IWindowImpl.cs
index cd84fc0f6d..83586d3e9f 100644
--- a/Perspex.Controls/Platform/IWindowImpl.cs
+++ b/Perspex.Controls/Platform/IWindowImpl.cs
@@ -6,7 +6,8 @@
 
 namespace Perspex.Platform
 {
-    using Perspex.Controls;
+    using System;
+    using System.Threading.Tasks;
 
     public interface IWindowImpl : ITopLevelImpl
     {
@@ -14,6 +15,8 @@ namespace Perspex.Platform
 
         void Show();
 
+        IDisposable ShowDialog();
+
         void Hide();
     }
 }
diff --git a/Perspex.Controls/TopLevel.cs b/Perspex.Controls/TopLevel.cs
index 2a3b19f13e..8cc0d46f74 100644
--- a/Perspex.Controls/TopLevel.cs
+++ b/Perspex.Controls/TopLevel.cs
@@ -24,6 +24,9 @@ namespace Perspex.Controls
         public static readonly PerspexProperty<Size> ClientSizeProperty =
             PerspexProperty.Register<TopLevel, Size>("ClientSize");
 
+        public static readonly PerspexProperty<bool> IsActiveProperty =
+            PerspexProperty.Register<Window, bool>("IsActive");
+
         private Dispatcher dispatcher;
 
         private IRenderManager renderManager;
@@ -113,6 +116,12 @@ namespace Perspex.Controls
             set { this.SetValue(ClientSizeProperty, value); }
         }
 
+        public bool IsActive
+        {
+            get { return this.GetValue(IsActiveProperty); }
+            private set { this.SetValue(IsActiveProperty, value); }
+        }
+
         public ILayoutManager LayoutManager
         {
             get;
@@ -140,6 +149,11 @@ namespace Perspex.Controls
             return this.PlatformImpl.PointToScreen(p);
         }
 
+        public void Activate()
+        {
+            this.PlatformImpl.Activate();
+        }
+
         protected IDisposable BeginAutoSizing()
         {
             this.autoSizing = true;
@@ -174,6 +188,7 @@ namespace Perspex.Controls
             }
 
             FocusManager.Instance.SetFocusScope(this);
+            this.IsActive = true;
         }
 
         private void HandleClosed()
@@ -186,6 +201,8 @@ namespace Perspex.Controls
 
         private void HandleDeactivated()
         {
+            this.IsActive = false;
+
             if (this.Deactivated != null)
             {
                 this.Deactivated(this, EventArgs.Empty);
diff --git a/Perspex.Controls/Window.cs b/Perspex.Controls/Window.cs
index 9ea156a08a..00605c7f36 100644
--- a/Perspex.Controls/Window.cs
+++ b/Perspex.Controls/Window.cs
@@ -7,6 +7,8 @@
 namespace Perspex.Controls
 {
     using System;
+    using System.Reactive.Linq;
+    using System.Threading.Tasks;
     using Perspex.Media;
     using Perspex.Platform;
     using Perspex.Styling;
@@ -17,6 +19,8 @@ namespace Perspex.Controls
         public static readonly PerspexProperty<string> TitleProperty =
             PerspexProperty.Register<Window, string>("Title", "Window");
 
+        private object dialogResult;
+
         static Window()
         {
             BackgroundProperty.OverrideDefaultValue(typeof(Window), Brushes.White);
@@ -43,6 +47,17 @@ namespace Perspex.Controls
             get { return typeof(Window); }
         }
 
+        public void Close()
+        {
+            this.PlatformImpl.Dispose();
+        }
+
+        public void Close(object dialogResult)
+        {
+            this.dialogResult = dialogResult;
+            this.Close();
+        }
+
         public void Hide()
         {
             using (this.BeginAutoSizing())
@@ -60,5 +75,31 @@ namespace Perspex.Controls
                 this.PlatformImpl.Show();
             }
         }
+
+        public Task ShowDialog()
+        {
+            return this.ShowDialog<object>();
+        }
+
+        public Task<TResult> ShowDialog<TResult>()
+        {
+            this.ExecuteLayoutPass();
+
+            using (this.BeginAutoSizing())
+            {
+                var modal = this.PlatformImpl.ShowDialog();
+                var result = new TaskCompletionSource<TResult>();
+
+                Observable.FromEventPattern(this, nameof(Closed))
+                    .Take(1)
+                    .Subscribe(_ =>
+                    {
+                        modal.Dispose();
+                        result.SetResult((TResult)this.dialogResult);
+                    });
+
+                return result.Task;
+            }
+        }
     }
 }
diff --git a/TestApplication/Program.cs b/TestApplication/Program.cs
index 4cc0d1f537..1221d69366 100644
--- a/TestApplication/Program.cs
+++ b/TestApplication/Program.cs
@@ -11,12 +11,11 @@ using Perspex.Layout;
 using Perspex.Media;
 using Perspex.Media.Imaging;
 using Perspex.Rendering;
-using Perspex.Styling;
 using Perspex.Threading;
 #if PERSPEX_GTK
 using Perspex.Gtk;
 #else
-using Perspex.Win32;
+using ReactiveUI;
 #endif
 using Splat;
 
@@ -189,7 +188,10 @@ namespace TestApplication
 
         private static TabItem ButtonsTab()
         {
-            return new TabItem
+            var showDialog = ReactiveCommand.Create();
+            Button showDialogButton;
+            
+            var result = new TabItem
             {
                 Header = "Buttons",
                 Content = new StackPanel
@@ -201,10 +203,11 @@ namespace TestApplication
                     MinWidth = 120,
                     Children = new Controls
                     {
-                        new Button
+                        (showDialogButton = new Button
                         {
                             Content = "Button",
-                        },
+                            Command = showDialog,
+                        }),
                         new Button
                         {
                             Content = "Button",
@@ -246,6 +249,31 @@ namespace TestApplication
                     }
                 },
             };
+
+            showDialog.Subscribe(async _ =>
+            {
+                var close = ReactiveCommand.Create();
+
+                var dialog = new Window
+                {
+                    Content = new StackPanel
+                    {
+                        Width = 200,
+                        Height = 200,
+                        Children = new Controls
+                        {
+                            new Button { Content = "Yes", Command = close, CommandParameter = "Yes" },
+                            new Button { Content = "No", Command = close, CommandParameter = "No" },
+                        }
+                    }
+                };
+
+                close.Subscribe(x => dialog.Close(x));
+
+                showDialogButton.Content =  await dialog.ShowDialog<string>();
+            });
+
+            return result;
         }
 
         private static TabItem TextTab()
@@ -582,6 +610,5 @@ namespace TestApplication
 
             return result;
         }
-
     }
 }
diff --git a/Windows/Perspex.Win32/Interop/UnmanagedMethods.cs b/Windows/Perspex.Win32/Interop/UnmanagedMethods.cs
index 2dde3b6a53..44e655fabd 100644
--- a/Windows/Perspex.Win32/Interop/UnmanagedMethods.cs
+++ b/Windows/Perspex.Win32/Interop/UnmanagedMethods.cs
@@ -516,6 +516,9 @@ namespace Perspex.Win32.Interop
         [DllImport("user32.dll", SetLastError = true)]
         public static extern bool DestroyWindow(IntPtr hwnd);
 
+        [DllImport("user32.dll")]
+        public static extern bool EnableWindow(IntPtr hWnd, bool bEnable);
+
         [DllImport("user32.dll")]
         public static extern bool EndPaint(IntPtr hWnd, ref PAINTSTRUCT lpPaint);
 
@@ -558,6 +561,9 @@ namespace Perspex.Win32.Interop
         [DllImport("user32.dll")]
         public static extern bool InvalidateRect(IntPtr hWnd, ref RECT lpRect, bool bErase);
 
+        [DllImport("user32.dll")]
+        public static extern bool IsWindowEnabled(IntPtr hWnd);
+
         [DllImport("user32.dll")]
         public static extern bool KillTimer(IntPtr hWnd, IntPtr uIDEvent);
 
@@ -579,6 +585,9 @@ namespace Perspex.Win32.Interop
         [DllImport("user32.dll")]
         public static extern bool ScreenToClient(IntPtr hWnd, ref POINT lpPoint);
 
+        [DllImport("user32.dll", SetLastError = true)]
+        public static extern IntPtr SetActiveWindow(IntPtr hWnd);
+
         [DllImport("user32.dll")]
         public static extern IntPtr SetCapture(IntPtr hWnd);
 
diff --git a/Windows/Perspex.Win32/WindowImpl.cs b/Windows/Perspex.Win32/WindowImpl.cs
index dbf138a459..25ffd322b4 100644
--- a/Windows/Perspex.Win32/WindowImpl.cs
+++ b/Windows/Perspex.Win32/WindowImpl.cs
@@ -7,9 +7,14 @@
 namespace Perspex.Win32
 {
     using System;
+    using System.Collections.Generic;
     using System.ComponentModel;
     using System.Diagnostics.CodeAnalysis;
+    using System.Linq;
+    using System.Reactive.Disposables;
+    using System.Reactive.Linq;
     using System.Runtime.InteropServices;
+    using System.Threading.Tasks;
     using Perspex.Controls;
     using Perspex.Input.Raw;
     using Perspex.Platform;
@@ -18,6 +23,8 @@ namespace Perspex.Win32
 
     public class WindowImpl : IWindowImpl
     {
+        private static List<WindowImpl> instances = new List<WindowImpl>();
+
         private UnmanagedMethods.WndProc wndProcDelegate;
 
         private string className;
@@ -31,6 +38,7 @@ namespace Perspex.Win32
         public WindowImpl()
         {
             this.CreateWindow();
+            instances.Add(this);
         }
 
         public Action Activated { get; set; }
@@ -83,6 +91,17 @@ namespace Perspex.Win32
             private set;
         }
 
+        public bool IsEnabled
+        {
+            get { return UnmanagedMethods.IsWindowEnabled(this.hwnd); }
+            set { UnmanagedMethods.EnableWindow(this.hwnd, value); }
+        }
+
+        public void Activate()
+        {
+            UnmanagedMethods.SetActiveWindow(this.hwnd);
+        }
+
         public IPopupImpl CreatePopup()
         {
             return new PopupImpl();
@@ -90,6 +109,7 @@ namespace Perspex.Win32
 
         public void Dispose()
         {
+            instances.Remove(this);
             UnmanagedMethods.DestroyWindow(this.hwnd);
         }
 
@@ -133,6 +153,37 @@ namespace Perspex.Win32
             UnmanagedMethods.ShowWindow(this.hwnd, UnmanagedMethods.ShowWindowCommand.Normal);
         }
 
+        public virtual IDisposable ShowDialog()
+        {
+            var disabled = instances.Where(x => x != this && x.IsEnabled).ToList();
+            TopLevel activated = null;
+
+            foreach (var window in disabled)
+            {
+                if (window.owner.IsActive)
+                {
+                    activated = window.owner;
+                }
+
+                window.IsEnabled = false;
+            }
+
+            this.Show();
+
+            return Disposable.Create(() =>
+            {
+                foreach (var window in disabled)
+                {
+                    window.IsEnabled = true;
+                }
+
+                if (activated != null)
+                {
+                    activated.Activate();
+                }
+            });
+        }
+
         protected virtual IntPtr CreateWindowOverride(ushort atom)
         {
             return UnmanagedMethods.CreateWindowEx(