I joined a thread of the month club and chose poly thread. Then I read where it can cut the fabric, so I called the company and said to change it to cotton. The gal said it was fine to use poly, but I kept thinking about it cutting my fabric so I told her to send me the cotton. She said with poly you don't get the lint. So, I'm undecided. I'm going to try the poly on one block and see how I like it. I'm reading where people say you can use either and I'm thinking that quilter's know best.