Normally I wear a medium shirt but as these were work shirts I went with the larger size. I ordered a large and they are just "a hair shy" of being too tight to be appropriate, but they are comfortable and of a nice quality. I do like the length of them as I have a long mid-drift(and prefer low to regular rise pants) and often find that if the shirt fits in the arm/chest area, it seems to barely meet the waist band of my pants. I would buy them again, possibly going to a larger size.