Hi Steve, That's exactly it. I realized after running the avwmerge manually that it was Seg Faulting every time. The problem was that my standard brain that i was registering to was about 32 megs. Thus, every cope that needed to be merged was also 32 megs, requiring about 2.5 gigs for a single avwmerge process. We resampled the standard image so that it is now about 4 megs and hopefully the avwmerge will only require about 1/8 of the ram it required previously. Thanks so much for your help! Tyler