diff --git a/dev/core/src/com/google/gwt/dev/shell/JavaScriptHost.java b/dev/core/src/com/google/gwt/dev/shell/JavaScriptHost.java
index 42eadf4..7d84f14 100644
--- a/dev/core/src/com/google/gwt/dev/shell/JavaScriptHost.java
+++ b/dev/core/src/com/google/gwt/dev/shell/JavaScriptHost.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2007 Google Inc.
+ * Copyright 2008 Google Inc.
  * 
  * Licensed under the Apache License, Version 2.0 (the "License"); you may not
  * use this file except in compliance with the License. You may obtain a copy of
@@ -37,8 +37,8 @@
     sHost.createNative(file, line, jsniSignature, paramNames, js);
   }
 
-  public static void exceptionCaught(int number, String name, String description) {
-    sHost.exceptionCaught(number, name, description);
+  public static void exceptionCaught(Object exception) {
+    sHost.exceptionCaught(exception);
   }
 
   /**
diff --git a/dev/core/src/com/google/gwt/dev/shell/JsniInjector.java b/dev/core/src/com/google/gwt/dev/shell/JsniInjector.java
index 50805f5..723eadc 100644
--- a/dev/core/src/com/google/gwt/dev/shell/JsniInjector.java
+++ b/dev/core/src/com/google/gwt/dev/shell/JsniInjector.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2007 Google Inc.
+ * Copyright 2008 Google Inc.
  * 
  * Licensed under the Apache License, Version 2.0 (the "License"); you may not
  * use this file except in compliance with the License. You may obtain a copy of
@@ -155,8 +155,8 @@
           + "  __static[\\\"@"
           + Jsni.JAVASCRIPTHOST_NAME
           + "::exceptionCaught"
-          + "(ILjava/lang/String;Ljava/lang/String;)\\\"]"
-          + "((e && e.number) || 0, (e && e.name) || null , (e && e.message) || null);\\n"
+          + "(Ljava/lang/Object;)\\\"]"
+          + "(e == null ? null : e);\\n"
           + "}\\n";
 
       /*
diff --git a/dev/core/src/com/google/gwt/dev/shell/ModuleSpace.java b/dev/core/src/com/google/gwt/dev/shell/ModuleSpace.java
index fcec6cf..e11d268 100644
--- a/dev/core/src/com/google/gwt/dev/shell/ModuleSpace.java
+++ b/dev/core/src/com/google/gwt/dev/shell/ModuleSpace.java
@@ -44,15 +44,13 @@
   }
 
   protected static RuntimeException createJavaScriptException(ClassLoader cl,
-      String name, String desc) {
+      Object exception) {
     Exception caught;
     try {
       Class<?> javaScriptExceptionClass = Class.forName(
           "com.google.gwt.core.client.JavaScriptException", true, cl);
-      Class<?> string = String.class;
-      Constructor<?> ctor = javaScriptExceptionClass.getDeclaredConstructor(new Class<?>[] {
-          string, string});
-      return (RuntimeException) ctor.newInstance(new Object[] {name, desc});
+      Constructor<?> ctor = javaScriptExceptionClass.getDeclaredConstructor(Object.class);
+      return (RuntimeException) ctor.newInstance(new Object[] {exception});
     } catch (InstantiationException e) {
       caught = e;
     } catch (IllegalAccessException e) {
@@ -134,20 +132,19 @@
     host.getClassLoader().clear();
   }
 
-  public void exceptionCaught(int number, String name, String message) {
+  public void exceptionCaught(Object exception) {
+    Throwable caught;
     Throwable thrown = sThrownJavaExceptionObject.get();
-
-    if (thrown != null) {
-      // See if the caught exception was thrown by us
-      if (isExceptionSame(thrown, number, name, message)) {
-        sCaughtJavaExceptionObject.set(thrown);
-        sThrownJavaExceptionObject.set(null);
-        return;
-      }
+    if (thrown != null && isExceptionSame(thrown, exception)) {
+      // The caught exception was thrown by us.
+      caught = thrown;
+      sThrownJavaExceptionObject.set(null);
+    } else if (exception instanceof Throwable) {
+      caught = (Throwable) exception;
+    } else {
+      caught = createJavaScriptException(getIsolatedClassLoader(), exception);
     }
-
-    sCaughtJavaExceptionObject.set(createJavaScriptException(
-        getIsolatedClassLoader(), name, message));
+    sCaughtJavaExceptionObject.set(caught);
   }
 
   /**
@@ -490,12 +487,11 @@
     throw thrown;
   }
 
-  @SuppressWarnings("unused")
-  protected boolean isExceptionSame(Throwable original, int number,
-      String name, String message) {
+  protected boolean isExceptionSame(@SuppressWarnings("unused")
+  Throwable original, Object exception) {
     // For most platforms, the null exception means we threw it.
     // IE overrides this.
-    return (name == null && message == null);
+    return exception == null;
   }
 
   protected String rebind(String sourceName) throws UnableToCompleteException {
diff --git a/dev/core/src/com/google/gwt/dev/shell/ShellJavaScriptHost.java b/dev/core/src/com/google/gwt/dev/shell/ShellJavaScriptHost.java
index f4e4821..23a8f6d 100644
--- a/dev/core/src/com/google/gwt/dev/shell/ShellJavaScriptHost.java
+++ b/dev/core/src/com/google/gwt/dev/shell/ShellJavaScriptHost.java
@@ -42,7 +42,7 @@
   /**
    * Call this when a JavaScript exception is caught.
    */
-  void exceptionCaught(int number, String name, String description);
+  void exceptionCaught(Object exception);
 
   /**
    * Invoke a native JavaScript function that returns a boolean value.
diff --git a/dev/core/super/com/google/gwt/dev/jjs/intrinsic/com/google/gwt/lang/Exceptions.java b/dev/core/super/com/google/gwt/dev/jjs/intrinsic/com/google/gwt/lang/Exceptions.java
index 63459d9..c437453 100644
--- a/dev/core/super/com/google/gwt/dev/jjs/intrinsic/com/google/gwt/lang/Exceptions.java
+++ b/dev/core/super/com/google/gwt/dev/jjs/intrinsic/com/google/gwt/lang/Exceptions.java
@@ -26,8 +26,7 @@
     if (e instanceof Throwable) {
       return e;
     }
-    return new JavaScriptException(javaScriptExceptionName(e),
-        javaScriptExceptionDescription(e));
+    return new JavaScriptException(e);
   }
 
   static boolean throwAssertionError() {
@@ -66,23 +65,5 @@
   static boolean throwAssertionError_Object(Object message) {
     throw new AssertionError(message);
   }
-
   // CHECKSTYLE_ON
-
-  /**
-   * Returns the description of an unexpected JavaScript exception (not a normal
-   * Java one).
-   */
-  private static native String javaScriptExceptionDescription(Object e) /*-{
-    return e.message;
-  }-*/;
-
-  /**
-   * Returns the name of an unexpected JavaScript exception (not a normal Java
-   * one).
-   */
-  private static native String javaScriptExceptionName(Object e) /*-{
-    return e.name;
-  }-*/;
-
 }
diff --git a/dev/windows/src/com/google/gwt/dev/shell/ie/ModuleSpaceIE6.java b/dev/windows/src/com/google/gwt/dev/shell/ie/ModuleSpaceIE6.java
index db77672..2ff7941 100644
--- a/dev/windows/src/com/google/gwt/dev/shell/ie/ModuleSpaceIE6.java
+++ b/dev/windows/src/com/google/gwt/dev/shell/ie/ModuleSpaceIE6.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2007 Google Inc.
+ * Copyright 2008 Google Inc.
  * 
  * Licensed under the Apache License, Version 2.0 (the "License"); you may not
  * use this file except in compliance with the License. You may obtain a copy of
@@ -25,6 +25,9 @@
 import org.eclipse.swt.ole.win32.OleAutomation;
 import org.eclipse.swt.ole.win32.Variant;
 
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
+
 /**
  * An implementation of {@link com.google.gwt.dev.shell.ModuleSpace} for
  * Internet Explorer 6.
@@ -74,13 +77,6 @@
     }
   }
 
-  // CHECKSTYLE_OFF
-  private static int CODE(int hresult) {
-    return hresult & 0xFFFF;
-  }
-
-  // CHECKSTYLE_ON
-
   private final OleAutomation window;
 
   /**
@@ -177,12 +173,35 @@
     return new IDispatchProxy(getIsolatedClassLoader());
   }
 
+  /**
+   * On IE6, we currently have no way of throwing arbitrary exception objects
+   * into JavaScript. What we throw in exception cases is an exception not under
+   * our exact control, so the best we can do is match descriptions to indicate
+   * a match. In practice this works well.
+   */
   @Override
-  protected boolean isExceptionSame(Throwable original, int number,
-      String name, String message) {
-    HResultException hre = new HResultException(original);
-    return CODE(hre.getHResult()) == CODE(number)
-        && hre.getMessage().equals(message);
+  protected boolean isExceptionSame(Throwable original, Object exception) {
+    Throwable caught;
+    try {
+      HResultException hre = new HResultException(original);
+      RuntimeException jse = createJavaScriptException(
+          getIsolatedClassLoader(), exception);
+      Method method = jse.getClass().getMethod("getDescription");
+      String description = (String) method.invoke(jse);
+      return hre.getMessage().equals(description);
+    } catch (SecurityException e) {
+      caught = e;
+    } catch (NoSuchMethodException e) {
+      caught = e;
+    } catch (IllegalArgumentException e) {
+      caught = e;
+    } catch (IllegalAccessException e) {
+      caught = e;
+    } catch (InvocationTargetException e) {
+      caught = e;
+    }
+    throw new RuntimeException(
+        "Failed to invoke JavaScriptException.getDescription()", caught);
   }
 
   private Variant execute(String code) {
diff --git a/user/src/com/google/gwt/core/client/JavaScriptException.java b/user/src/com/google/gwt/core/client/JavaScriptException.java
index b4b26b1..bf9a9e5 100644
--- a/user/src/com/google/gwt/core/client/JavaScriptException.java
+++ b/user/src/com/google/gwt/core/client/JavaScriptException.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2006 Google Inc.
+ * Copyright 2008 Google Inc.
  * 
  * Licensed under the Apache License, Version 2.0 (the "License"); you may not
  * use this file except in compliance with the License. You may obtain a copy of
@@ -24,11 +24,72 @@
  */
 public final class JavaScriptException extends RuntimeException {
 
+  private static String constructMessage(Object e) {
+    return "(" + getName(e) + "): " + getDescription(e) + getProperties(e);
+  }
+
+  private static String getDescription(Object e) {
+    if (e instanceof JavaScriptObject) {
+      return getDescription0((JavaScriptObject) e);
+    } else {
+      return e + "";
+    }
+  }
+
+  private static native String getDescription0(JavaScriptObject e) /*-{
+    if (e == null) {
+      return null;
+    }
+    return e.message == null ? null : e.message;
+  }-*/;
+
+  private static JavaScriptObject getException(Object e) {
+    if (e instanceof JavaScriptObject) {
+      return (JavaScriptObject) e;
+    } else {
+      return null;
+    }
+  }
+
+  private static String getName(Object e) {
+    if (e == null) {
+      return "null";
+    } else if (e instanceof JavaScriptObject) {
+      return getName0((JavaScriptObject) e);
+    } else if (e instanceof String) {
+      return "String";
+    } else {
+      return e.getClass().getName();
+    }
+  }
+
+  private static native String getName0(JavaScriptObject e) /*-{
+    if (e == null) {
+      return null;
+    }
+    return e.name == null ? null : e.name;
+  }-*/;
+
+  private static String getProperties(Object e) {
+    if (e instanceof JavaScriptObject) {
+      return getProperties0((JavaScriptObject) e);
+    } else {
+      return null;
+    }
+  }
+
   /**
-   * The original type name of the JavaScript exception this class wraps,
-   * initialized as <code>e.name</code>.
+   * Returns the list of properties of an unexpected JavaScript exception.
    */
-  private final String name;
+  private static native String getProperties0(JavaScriptObject e) /*-{
+    var result = "";
+    for (prop in e) {
+      if (prop != "name" && prop != "description") {
+        result += "\n " + prop + ": " + e[prop];
+      }
+    }
+    return result;
+  }-*/;
 
   /**
    * The original description of the JavaScript exception this class wraps,
@@ -37,35 +98,65 @@
   private final String description;
 
   /**
-   * @param name the original JavaScript type name of the exception
-   * @param description the original JavaScript message of the exception
+   * The underlying exception this class wraps.
    */
+  private final JavaScriptObject exception;
+
+  /**
+   * The original type name of the JavaScript exception this class wraps,
+   * initialized as <code>e.name</code>.
+   */
+  private final String name;
+
+  /**
+   * @param exception
+   */
+  public JavaScriptException(Object e) {
+    super(constructMessage(e));
+    this.name = getName(e);
+    this.description = getDescription(e);
+    this.exception = getException(e);
+  }
+
   public JavaScriptException(String name, String description) {
     super("JavaScript " + name + " exception: " + description);
     this.name = name;
     this.description = description;
+    this.exception = null;
   }
 
   /**
-   * Useful for server-side instantiation.
+   * Used for server-side instantiation during JUnit runs. Exceptions are
+   * manually marshaled through
+   * {@link com.google.gwt.junit.client.impl.ExceptionWrapper} objects.
    * 
-   * @param message the detail message.
+   * @param message the detail message
    */
   protected JavaScriptException(String message) {
     super(message);
     this.name = null;
     this.description = message;
+    this.exception = null;
   }
 
   /**
-   * @return the original JavaScript message of the exception
+   * Returns the original JavaScript message of the exception; may be
+   * <code>null</code>.
    */
   public String getDescription() {
     return description;
   }
 
   /**
-   * @return the original JavaScript type name of the exception
+   * Returns the original JavaScript the exception; may be <code>null</code>.
+   */
+  public JavaScriptObject getException() {
+    return exception;
+  }
+
+  /**
+   * Returns the original JavaScript type name of the exception; may be
+   * <code>null</code>.
    */
   public String getName() {
     return name;
diff --git a/user/test/com/google/gwt/core/CoreSuite.java b/user/test/com/google/gwt/core/CoreSuite.java
new file mode 100644
index 0000000..17c5806
--- /dev/null
+++ b/user/test/com/google/gwt/core/CoreSuite.java
@@ -0,0 +1,36 @@
+/*
+ * Copyright 2008 Google Inc.
+ * 
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ * 
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * 
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package com.google.gwt.core;
+
+import com.google.gwt.core.client.JavaScriptExceptionTest;
+import com.google.gwt.junit.tools.GWTTestSuite;
+
+import junit.framework.Test;
+
+/**
+ * All I18N tests.
+ */
+public class CoreSuite {
+  public static Test suite() {
+    GWTTestSuite suite = new GWTTestSuite("All core tests");
+
+    // $JUnit-BEGIN$
+    suite.addTestSuite(JavaScriptExceptionTest.class);
+    // $JUnit-END$
+
+    return suite;
+  }
+}
diff --git a/user/test/com/google/gwt/core/client/JavaScriptExceptionTest.java b/user/test/com/google/gwt/core/client/JavaScriptExceptionTest.java
new file mode 100644
index 0000000..6397c5b
--- /dev/null
+++ b/user/test/com/google/gwt/core/client/JavaScriptExceptionTest.java
@@ -0,0 +1,144 @@
+/*
+ * Copyright 2008 Google Inc.
+ * 
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ * 
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * 
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package com.google.gwt.core.client;
+
+import com.google.gwt.junit.client.GWTTestCase;
+
+/**
+ * Any JavaScript exceptions occurring within JSNI methods are wrapped as this
+ * class when caught in Java code. The wrapping does not occur until the
+ * exception passes out of JSNI into Java. Before that, the thrown object
+ * remains a native JavaScript exception object, and can be caught in JSNI as
+ * normal.
+ */
+public class JavaScriptExceptionTest extends GWTTestCase {
+
+  static native JavaScriptObject makeJSO() /*-{
+    return {
+      toString:function() {
+        return "jso";
+      },
+      name: "myName",
+      message: "myDescription",
+      extraField: "extraData"
+    };
+  }-*/;
+
+  static void throwJava(Throwable t) throws Throwable {
+    throw t;
+  }
+
+  static native void throwNative(Object e) /*-{
+    throw e;
+  }-*/;
+
+  static void throwSandwichJava(Object e) {
+    throwNative(e);
+  }
+
+  static native void throwSandwichNative(Throwable t) /*-{
+    @com.google.gwt.core.client.JavaScriptExceptionTest::throwJava(Ljava/lang/Throwable;)(t);
+  }-*/;
+
+  /**
+   * This test doesn't work in hosted mode yet; we'd need a way to throw true
+   * native objects as exceptions. Windows/IE is the deal killer right now on
+   * really making this work since there's no way to raise an exception of a
+   * true JS value. We could use JS lambdas around Java calls to get around this
+   * restriction.
+   */
+  public native void disabledTestJsExceptionSandwich() /*-{
+    var e = { };
+    try {
+      @com.google.gwt.core.client.JavaScriptExceptionTest::throwSandwichJava(Ljava/lang/Object;)(e);
+    } catch (t) {
+      @junit.framework.Assert::assertSame(Ljava/lang/Object;Ljava/lang/Object;)(e, t);
+    }
+  }-*/;
+
+  @Override
+  public String getModuleName() {
+    return "com.google.gwt.core.Core";
+  }
+
+  public void testJavaExceptionSandwich() {
+    RuntimeException e = new RuntimeException();
+    try {
+      throwSandwichNative(e);
+    } catch (Throwable t) {
+      assertSame(e, t);
+    }
+  }
+
+  public void testJso() {
+    JavaScriptObject jso = makeJSO();
+    try {
+      throwNative(jso);
+      fail();
+    } catch (JavaScriptException e) {
+      assertEquals("myName", e.getName());
+      assertEquals("myDescription", e.getDescription());
+      assertSame(jso, e.getException());
+      assertTrue(e.getMessage().contains("myName"));
+      assertTrue(e.getMessage().contains("myDescription"));
+      assertTrue(e.getMessage().contains("extraField"));
+      assertTrue(e.getMessage().contains("extraData"));
+    }
+  }
+
+  public void testNull() {
+    try {
+      throwNative(null);
+      fail();
+    } catch (JavaScriptException e) {
+      assertEquals("null", e.getName());
+      assertEquals("null", e.getDescription());
+      assertEquals(null, e.getException());
+      assertTrue(e.getMessage().contains("null"));
+    }
+  }
+
+  public void testObject() {
+    Object o = new Object() {
+      @Override
+      public String toString() {
+        return "myLameObject";
+      }
+    };
+    try {
+      throwNative(o);
+      fail();
+    } catch (JavaScriptException e) {
+      assertEquals(o.getClass().getName(), e.getName());
+      assertEquals("myLameObject", e.getDescription());
+      assertEquals(null, e.getException());
+      assertTrue(e.getMessage().contains(o.getClass().getName()));
+      assertTrue(e.getMessage().contains("myLameObject"));
+    }
+  }
+
+  public void testString() {
+    try {
+      throwNative("foobarbaz");
+      fail();
+    } catch (JavaScriptException e) {
+      assertEquals("String", e.getName());
+      assertEquals("foobarbaz", e.getDescription());
+      assertEquals(null, e.getException());
+      assertTrue(e.getMessage().contains("foobarbaz"));
+    }
+  }
+}