I don't prewash my any of fabrics, never have and I don't have any problems with shrinkage or bleeding. However, somewhere on here awhile back, we were discussing this and the fear of bedbugs and other such unwelcome critters were brought up. Since our fabric comes from all over the world now, I still don't wash mine, but, I do place it in the freezer for 24hrs, to make sure anything that wasn"t supposed to be in there is dead. Freezing your fabric does not harm the fabric, colours do not bleed and it is guaranteed to kill even the most smallest bug. Better safe than sorry, especially now that we are all checking out thrift shops, yard sales and goodwills for our fabric deals.