I always pre-wash. Then after the quilt is done I wash again. Recently I had a lot of new fabric that I washed before cutting (am I glad I did). One of the aqua cotton pieces bleed like crazy. It never would have entered my mind that this fabric would bleed. I have used this color before with no problems. Most of the other fabrics that were in the wash were not affected but one of the white pieces turned a light blue where the white was. I then put that piece in the wash again with my white clothes and Oxyclean and all the blue came out. I took the bleeder into the house and soaked it in hot water still bleed, I did this about three times and it continued to bleed. I then soaked in the hot water with Retayne and the bleeding stoped. I will always pre-wash. BrendaK