Plastic, because I clean out my bunny's litter box with them! BTW, does anyone want two house bunnies? They are very friendly. Can't keep because we just got a greyhound and the bunnies are afraid of her! They're FREE!
Mine is plastic but my 95 yr old aunts is both. She gets the paper bags put inside the plastic ones. Her bags look much stronger and don't bulge all over like mine.
Donna