They're described as being 100% cotton, but they feel like a cotton polyester mix.  I hate that type of fabric.  They also fit further below the waist than I like - I like just below the belli button, and these fit a good 3 inches below, so I would worry about keeping them on.  The waist was very large, while the hips were tight - not really what I would expect from a relaxed fit.  The fit of the carpenter duck pants was much better for me (in a size smaller), and they felt like 100% cotton, so I sent these back and ordered another pair of the carpenter duck pants.