I read some other reviews of sizes being too big, etc, but that was not my experience.  I am a size 4-6 (5'6", 130lbs) and bought a small and it's perfect.  It's also shaped even better than I think it shows in the picture.  Plus, I have worn it now at 17 degrees and was pleasantly surprised how warm it is (didn't really buy it for cold,cold weather).  But it is majority wool, so that's nice.