I bought these online, and opted for the assorted colors pack. When they arrived, the package said, in small print, "heather variety 25% polyester". When I checked the waistbands, sure enough, they said 25% polyester. Now, when I buy cotton clothing, I expect it to be, um, COTTON. Or at least be warned before I send for them. So back they went. I'll shop where I can inspect the packaging from now on.