I think it will handle any regular 2.5 inch hard drive. Right now the bigger that exists is a 320 gig western digital. I know there are 2 thicknesses though, and the macbook takes only the thinner of the two (how thick it is, I have no clue). Anyhow I wouldnt count on 1 terabyte, but I did hear about technologies in doubling 2.5 inch hard drive memory capacities. So maybe something around 600-750 gigs might be made.