Robin, I would imagine that any 2.5 inch mobile harddrive will fit into the new MacBook Pro. The only question in my mind would be what kind of power would it draw (can the power supply deal with it) and what kind of heat would it throw off(will it be too hot to handle.) I would recommend a Seagate Momentus 160 GB 5400rpm. This drive carries a 5 year warranty. The 5400 rpm feels much faster than the 4200 rpm drives; the 5400 has a much lower power consumption than the faster drives - battery lasts longer, and it doesn't seem as hot to me (I often use my Ti with it setting on my lap - I have the 100GB 5400rpm.) The Seagate Momentus drives are quick, sturdy, and quiet. External drives are also easy to use. Just plug them in. The small ones are easy to carry around. Something tells me if you are filling up a 100GB and having space problems, you will fill up a 160GB sooner or later. You really might want to consider an external drive rather than just installing a larger drive. If you do install a larger internal drive, put your old drive into an external case and continue to use it. You can never have too much hard drive space. Paula Robin writes: <<My current PowerBook has a 100Gb drive and I am constantly battling to maintain 8Gb-10Gb of spare space. While I could get the 120Gb, 160Gb would give me a lot more elbo room. Does anyone know if a 160Gb will fit?>>