During fracture-stimulation treatments, particle-laden slurries may damage pumping equipment and have been shown to erode perforation tunnels. During subsequent flowback operations, minor to severe erosion of surface equipment may be observed if formation sand and/or proppants are produced. This paper compares the erosivity of sand-based and ceramic proppants. The erosion mechanisms are examined, and theoretical and laboratory measurements are in agreement that low-density ceramic proppants, because of roundness and sphericity, are less erosive than more-angular sand products.