Bought for my husband for upcoming trip.  He is 5'8 and wears a size 36 pants.  He prefers XL tops to large, so I went up a size.  The XL looks great and is the perfect size for anyone 5'8-6 that prefers extra room-he loves it.  We tried it on with a Sherpa lined fleece and it was the perfect size for layering for our trip.  If you want something truer to size or to wear in the summer, size L would be perfect with thinner layers.