I will be the first to admit that I don't usually pre-wash my fabric but after a discussion here on the board re batik's and running/bleeding - I was about to start a quilt using batiks for the first time - OK I thought I will wash (by hand) and see what happens - am I glad I did - I couldn't believe how much colour came out and the number of times I had to wash to get the water to run clear. So I would suggest that, at least with batik fabric, it should be pre-washed.