Is IDisposable.Dispose() called automatically?

Possible Duplicate:
Will the Garbage Collector call IDisposable.Dispose for me?

I have a Class which has some unmanaged resources. My class implements the IDisposable interface and releases the unmanaged resources in the Dispose() method. Do I have to call the Dispose() method or will it be automatically called somehow? Will the Garbage Collector call it?