This is not my first pair of Champion workout pants.  They usually run true to size, if not a little bigger.  Medium seems to be just a little too big for me in the waist, but I am afraid to buy size small because I like the length of size medium since I am 5ft. 8.  They feel cool, even after a couple of hours of workout.  The only complaint I have is that I have to pull them up frequently during Pilates classes, because they are sliding down.