Depends on the batting and the look I want. Polyester batting doesn't need pre-washing. With cotton and cotton/blend, if you like the antique look of a crinkled quilt then don't wash the batting first. If you want more of a contemporary, smooth looking quilt, then you will want to pre-wash. Of course when I say wash, I mean soak, rinse and dry. Most batting shouldn't be agitated much at all before quilting.