The only patagonia bottoms I have are the capilene bottoms, and those run pretty much normal sized. The Small definitely fits perfectly. And I usually wear a 2-4 in anyone else's sizes (but Patagonia non-stretchy stuff doesn't allow for round bottoms so I don't buy it) and an XS in Patagonia dresses/tops (mostly b/c the chest would be too big if I tried a small)