diff --git a/butterflow-ui/ButterflowWrapper.cs b/butterflow-ui/ButterflowWrapper.cs
index c9d3564..1fe2b20 100644
--- a/butterflow-ui/ButterflowWrapper.cs
+++ b/butterflow-ui/ButterflowWrapper.cs
@@ -24,6 +24,8 @@ namespace butterflow_ui
         private Lazy<string> executablePath = new Lazy<string>(() => Path.Combine(Directory.GetCurrentDirectory(), "ThirdPartyCompiled", "butterflow.exe"));
         /// <summary> The console output from butterflow. </summary>
         private string consoleOutput = string.Empty;
+        /// <summary> True if butterflow is running, false if not. </summary>
+        private bool isRunning;
         /// <summary> Event queue for all listeners interested in ParsedConsoleOutputRecieved events. </summary>
         public event EventHandler<ButterflowOutputArgs> ParsedConsoleOutputRecieved;
 
@@ -46,6 +48,21 @@ namespace butterflow_ui
             }
         }
 
+        /// <summary> Gets or sets a value indicating whether butterflow is currently running. </summary>
+        /// <value> True if butterflow is running, false if not. </value>
+        public bool IsRunning
+        {
+            get
+            {
+                return this.isRunning;
+            }
+            set
+            {
+                this.isRunning = value;
+                OnPropertyChanged();
+            }
+        }
+
         #endregion
 
         #region Methods
@@ -71,20 +88,34 @@ namespace butterflow_ui
         /// <param name="arguments">     Options for controlling the operation. </param>
         private void Run(string arguments)
         {
-            var process = new Process();
-            process.StartInfo = new ProcessStartInfo(executablePath.Value, arguments);
+            if (!this.IsRunning)
+            {
+                var process = new Process();
+                process.StartInfo = new ProcessStartInfo(executablePath.Value, arguments);
 
-            process.StartInfo.CreateNoWindow = true;
-            process.StartInfo.UseShellExecute = false;
-            process.StartInfo.RedirectStandardOutput = true;
-            process.StartInfo.RedirectStandardError = true;
-            process.EnableRaisingEvents = true;
-            process.OutputDataReceived += Process_OutputDataReceived;
-            process.ErrorDataReceived += Process_OutputDataReceived;
+                process.StartInfo.CreateNoWindow = true;
+                process.StartInfo.UseShellExecute = false;
+                process.StartInfo.RedirectStandardOutput = true;
+                process.StartInfo.RedirectStandardError = true;
+                process.EnableRaisingEvents = true;
+                process.OutputDataReceived += Process_OutputDataReceived;
+                process.ErrorDataReceived += Process_OutputDataReceived;
+                process.Exited += Process_Exited;
 
-            process.Start();
-            process.BeginOutputReadLine();
-            process.BeginErrorReadLine();
+                process.Start();
+                process.BeginOutputReadLine();
+                process.BeginErrorReadLine();
+
+                this.IsRunning = true;
+            }
+        }
+
+        /// <summary> Event handler. Called by Process for exited events. </summary>
+        /// <param name="sender"> Source of the event. </param>
+        /// <param name="e">      Event information. </param>
+        private void Process_Exited(object sender, EventArgs e)
+        {
+            this.IsRunning = false;
         }
 
         /// <summary>
diff --git a/butterflow-ui/InverseBoolConverter.cs b/butterflow-ui/InverseBoolConverter.cs
new file mode 100644
index 0000000..989e776
--- /dev/null
+++ b/butterflow-ui/InverseBoolConverter.cs
@@ -0,0 +1,57 @@
+using System;
+using System.Collections.Generic;
+using System.Globalization;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using System.Windows.Data;
+
+namespace butterflow_ui
+{
+    /// <summary> An inverse boolean converter. </summary>
+    [ValueConversion(typeof(bool), typeof(bool))]
+    public class InverseBoolConverter : IValueConverter
+    {
+        /// <summary> Converts a boolean to its inverse. </summary>
+        /// <exception cref="InvalidCastException"> Thrown when an object cannot be cast to a required
+        ///                                         type. </exception>
+        /// <param name="value">      The value produced by the binding source. </param>
+        /// <param name="targetType"> The type of the binding target property. </param>
+        /// <param name="parameter">  The converter parameter to use. </param>
+        /// <param name="culture">    The culture to use in the converter. </param>
+        /// <returns>
+        /// A converted value. If the method returns <see langword="null" />, the valid null value is
+        /// used.
+        /// </returns>
+        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
+        {
+            if(targetType == typeof(bool))
+            {
+                return !(bool)value;
+            }
+
+            throw new InvalidCastException(string.Format("Cannot convert type {0} to boolean.", targetType.Name));
+        }
+
+        /// <summary> Converts an inverse boolean back to its original state. </summary>
+        /// <exception cref="InvalidCastException"> Thrown when an object cannot be cast to a required
+        ///                                         type. </exception>
+        /// <param name="value">      The value that is produced by the binding target. </param>
+        /// <param name="targetType"> The type to convert to. </param>
+        /// <param name="parameter">  The converter parameter to use. </param>
+        /// <param name="culture">    The culture to use in the converter. </param>
+        /// <returns>
+        /// A converted value. If the method returns <see langword="null" />, the valid null value is
+        /// used.
+        /// </returns>
+        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
+        {
+            if (targetType == typeof(bool))
+            {
+                return !(bool)value;
+            }
+
+            throw new InvalidCastException(string.Format("Cannot convert type {0} to boolean.", targetType.Name));
+        }
+    }
+}
diff --git a/butterflow-ui/MainWindow.xaml b/butterflow-ui/MainWindow.xaml
index 8978095..fbf169a 100644
--- a/butterflow-ui/MainWindow.xaml
+++ b/butterflow-ui/MainWindow.xaml
@@ -23,6 +23,7 @@
                 <x:Type TypeName="butterflow_ui:FlowFilterType"/>
             </ObjectDataProvider.MethodParameters>
         </ObjectDataProvider>
+        <butterflow_ui:InverseBoolConverter x:Key="InverseBoolConverter" />
     </Window.Resources>
     <DockPanel>
         <Menu DockPanel.Dock="Top">
@@ -102,7 +103,7 @@
                     </Grid>
                 </GroupBox>
             </StackPanel>
-            <Button Grid.Column="4" Grid.Row="0" Name="btnProcess" ToolTip="{x:Static loc:Localization.ProcessTooltip}" Click="btnProcess_Click">
+            <Button Grid.Column="4" Grid.Row="0" Name="btnProcess" ToolTip="{x:Static loc:Localization.ProcessTooltip}" IsEnabled="{Binding ButterflowWrapper.IsRunning, Mode=OneWay, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type butterflow_ui:MainWindow}}, UpdateSourceTrigger=PropertyChanged, Converter={StaticResource InverseBoolConverter}}" Click="btnProcess_Click">
                 <StackPanel>
                     <ContentControl MaxWidth="32" HorizontalAlignment="Center" Name="btnRun" Template="{StaticResource RadarIcon}" />
                     <Label Content="{x:Static loc:Localization.ProcessLabel}" />
diff --git a/butterflow-ui/butterflow-ui.csproj b/butterflow-ui/butterflow-ui.csproj
index cc232c0..3481b96 100644
--- a/butterflow-ui/butterflow-ui.csproj
+++ b/butterflow-ui/butterflow-ui.csproj
@@ -61,6 +61,7 @@
       <SubType>Designer</SubType>
     </ApplicationDefinition>
     <Compile Include="FlowFilterType.cs" />
+    <Compile Include="InverseBoolConverter.cs" />
     <Compile Include="PropertyChangedAlerter.cs" />
     <Compile Include="RegionType.cs" />
     <Page Include="Icons.xaml">