I have used the all cotton but have also used the poly-cotton blends with no problems. In fact one day, I forgot to change thread and pieced a bunch of blocks before I realized that the thread I was using was the serger thread from Joann's that is normally $1.99, on sale for 99¢, and have had no problems. I washed the tops, quilted them, they are in great shape. I do like the Egyptian cotton from Connecting Threads. Yes it is a little linty but what thread doesn't have some.