I've only used cotton thread, but just joined a thread of the month club and received 5 polyester spools of pretty thread. I've written them to ask them to change it to cotton, but they haven't responded. I hate to waste $40 worth of thread. I don't garment sew and can't afford not to use them. They say they "saw" your cotton fabric. But then other people say it's fine. I am so confused. But I'm for sure going to call the month of the club co. and change my thread preference tomorrow. Oh, by the way, does anyone know how to bookmark a page? I have no idea how to, but would really like to on some pages with good tips. Thanks, Jeanne