I do wash first especially the ones that may bleed. Think about this though.....if you wash part of the fabrics and not the rest, shrinkage may be a factor after the quilt is completed and then washed. So another reason I like to wash all fabrics before using. With the exception of my 30's fabrics, as I love the crinkled look you get from not prewashing, but waiting to wash after the quilt is quilted. It really is a preference thing I guess. Since there are no real quilt police, it is your quilt, you do what you feel best.