Never heard of any sort of limit on the file attachment size nor the downloaded file size as well. I've sent numerous 4 to 5 minute video files to my BB all the time, so I'm uncertain if there is a limit or not, however, I would strongly suggest getting one of the larger Micro SD cards 2GB at least, if you plan on downloading a lot of larger files. You will definitely need it due to the limited device memory. I'll see if I can find anything etched in stone about the max file sizes.