This jacket is nice! After reading reivews on several different sites regarding the slim fit, I decided to order a medium. I have an Arcteryx Alpha SL, Alpha LT, Beta SL, and Atom LT--all size small. I'm 5'4" and 105lbs. Turns out the medium is just right. It's only slightly large around the hem, but can be adjusted with the elastic bungie. I'm sure I could wear a small, but I wanted this to fit like a jacket, not a sweater. I don't like form-fitting clothes. If you do, then go with your regular size. The jacket is beautiful and feels great on. I can hardly wait for fall!