Frans points out that in the current version of VB.NET you can't re-implement an interface that your base class implements. Although reimplementing a base interface isn't a common scenario, there are some times (such as the one that Frans outlines) where it is needed. Although I don't know whether this is in the PDC build or not, I don't think it's much of a revelation to say that the Whidbey version of VB will allow interface reimplementation. Doesn't help now, but...