Light optical and scanning electron microscope studies were conducted to characterize the erosion resistances of polymethyl methacrylate (PMMA), polycarbonate (PC), polytetrafluoroethylene (PTFE), and ultrahigh-molecular-weight polyethylene (UHMWPE). Erosion was caused by a jet of spherical microglass beads at normal impact. During the initial stages of damage, the surfaces of these materials were studied using a profilometer. Material buildup above the original surface was observed on PC and PMMA. As erosion progressed, this buildup disappeared as the pit became deeper. Little or no buildup was observed on PTFE and on UHMWPE. UHMWPE and PTFE are the most resistant materials and PMMA the least. Favorable properties for high erosion resistance seem to be high values of ultimate elongation, and strain energy and a low value of the modulus of elasticity. Erosion rate versus time curves of PC and PTFE exhibit incubation, acceleration, and steady-state periods. A continuously increasing erosion rate period was observed, however, for PMMA instead of a steady-state period. At early stages of damage and at low impact pressures, material removal mechanisms appear to be similar to those for metallic materials. “Flakelike” debris was observed on the surface which is indicative of deformation wear by repeated impact and eventual fatigue, causing material loss. At higher impact pressures, evidence of melting of the surface was noted, which is believed to be the result of heat generated by impact.Presented as an American Society Of Lubrication Engineers paper at the ASLE/ASME Lubrication Conference in Hartford, Connecticut, October 18–20, 1983