the description reads: Constructed of 600 thread count cotton... they just arrived... cotton and polyester. I would NEVER have bought sheets that weren't pure cotton. They are being returned tomorrow, and I am out the cost of shipping a HEAVY package back. When I was trying to figure out how to write this review I saw 'fine print' at the bottom of the page that does indicate cotton and polyester. But I trusted the product description. VERY disappointed in Overstocks!