XS sizing
I am 5'1", 110 lbs and bought the XS. It's actually an extra inch or so too long for me, but overall a VERY close fit considering the other options I tried on. I figured I'd add to the other reviews who all seem to be looking for petite pants! The pants are cute and comfy. I would definitely recommend them. I bought them for an 8-week trip throughout Africa and Europe.

Comfortable Lightweight Hiking/Summer Pant
This is a lightweight comfortable pant good for warm days. I am 5'5 and 105 pounds and ordered the XS which fit well. Your satisfaction with the length may depend on how you wear the pants. If you wear these at true waist level (at or slightly above your navel), they would have been too short as noted by a previous reviewer. I wear them more atop my hips as they are slightly big if I wear them at my true waist, so the length was perfect for me. The built in belt allows you to cinch them high or low, but there is no give in the waist, so these fit true to size. An XS is a true size 2. There is a comfortable amount of room in the legs allowing freedom of movement without excessive bagginess. The front pockets are deep, but there are no zippers, buttons, or other closures on any of the pockets for more secure fastening of contents. The pants have roll-up fasteners on both sides of the pant leg which is nice because sometimes these types of pants only secure on one side which sometimes leads to the one side staying up while the other side comes down especially when you are very active. When the pants are rolled up, they come to about 1.5 inches below my knee level. I liked them so much I bought a second pair.

XS is for very short people!
I am 5'1", 104 lbs and wear petite sizes (0 petite), and always need the "short" versions of other brands of outdoor pants (The North Face, for example). From the Outdoor Research size chart, it seemed like I'd fit perfectly into the XS, but they were actually too short for me! That's literally never happened to me before. However, if you are very petite and have always had trouble finding short enough outdoor pants, these would be the ones for you! The fabric is very comfortable and they are otherwise great pants, they fit me well in the waist.

AMAZING
A lighter fabric than what I expected, but none the less amazing. Great cut & feel! Breathes great and never restricts motion. I plan on getting several more pair in different colors. The peat is a great forest green color.