It depends on how it is going to be quilted and the look you want. I personally like close intricate quilting and like the little bit of puffiness that I get without washing before quilting. But if you are going to tie your quilts or do quilting with large spaces I would wash first. But keep in mind if you wash your fabric - particularly backing fabric - you may experience considerable shrinkage (like 6")......ask me how I know this.....lol. Bought 3 yards of 108" wide backing fabric that shrunk so much it wouldn't fit my 103" wide quilt....lol. Thank God for Charisma who came to the rescue and added some fabric to make it work!