My Aperture library had been growing immensely over the last 3 years even though I had been diligently maintaining the gallery with only my best images, deleting most of the fluff. I peered into the Aperture Library and I found something curious. Some projects with just a few photos had thumbnail files over 100MB! It turns out that Aperture doesn't delete thumbnails when you delete a photo. What's more is that thumbnails are fairly large and are generated as 3 different files. If you're like me, you shoot a lot of photos and often delete many more than you keep. I shoot on average 600 photos per week, all of which are loaded into Aperture. Once I sweep the project, I end up with somewhere between 30 to 50% of the total of photos shot. This means that files pertaining to 300 junk photos per week are being left in my Aperture library and have been accumulating orphan thumbnail files. I'm using Aperture 2 so I hope that Apple has fixed this very glaring problem in Aperture 3. In the meantime, I set out to delete all the thumbnail files so that new ones could be generated without the deleted photos. Instead of going through every single project and deleting these files, I ran the following Terminal commands: note: Before performing these commands, backup your Aperture library find ~/Pictures -name "AP.Thumbnails" -delete find ~/Pictures -name "AP.Minis" -delete find ~/Pictures -name "AP.Tinies" -delete Result? I saved over 60GB which is like gold on my MacBook Pro. My Aperture library went from 250GB to 189GB.