First off, thanks all for such useful bridging software. I converged on this after seeing leaks in my interactions with a DLL. My actual leak seems to occur on cast/unbox. However, in understanding what I may or may not be doing wrong, I present this situation: (loop for i from 0 do (rdnzl::invoke (rdnzl::invoke "System.Guid" "NewGuid") "ToString")) Nothing particularly inherent to Guids, just an example I could find that returns a string. This loop sits there eating up Ram in a situation where I'm guessing it shouldn't. Putting garbage collects in the middle of its execution doesn't change this, nor does running GC/clean-down after breaking out. I'm talking about post-collect menory usage continously rising. It stereotypes a situation in my usage pattern of calling into dotnet and returning strings. Is there something I'm doing wrong? An incorrect assumption about dotnet? Any help appreciated. Thanks, Matt