I am 5'9 and 155 lbs...I debated ordering a medium or a large. Well, I ordered a medium and received a size small. The size small is a tad bit snugger in the thigh area than I'd like, but actually fits well enough that I decided to keep and wear them. If I were to order another pair, I still think I'd try to go with a size medium though. That being said, these seem well made and like they will hold up well. They are soft and comfortable, and I always like having pockets for my phone or whatever else!