That is indeed what Tess is saying, but she also says "that is what happens when you get an OutOfMemoryException". The other party claims the garbage collector will perform defragmentation (which is part of garbage collection, after all) before throwing OutOfMemoryException, and if that is true you wouldn't get OOM as long as the new allocation requires less than total free memory. If so, the only time you should get the exception should be when the live objects are pinned. (Very large objects are said to be "pinned" because they are never moved in defragmentation due to the hard work it would be moving such big objects around.) I guess if you want very much to conclude that they both are right you could assume Tess was talking about pinned objects, but that is a rather contrived way of getting there, and I frankly don't see the point. For me the important thing isn't who is right but what the fact is. And that is unfortunately still no more clear for me.