And...of course, it would be rally nice that this is done by implementing the protocol #cleanUp: and #cleanUp Check issue http://code.google.com/p/pharo/issues/detail?id=2130 At some point, we will be able to do Smalltalk cleanUp and this propagate the message to all clases. For the moment, just implementing your cleaning in those methods, and calling them from cleanUpForRelease would be enough. Cheers mariano