The objective of this work was to understand the influence of grain size on solid impingement erosion behavior characterized by deformation at high strain rates and large strains. Experiments were carried out at a velocity of 40 m/s, impact angle of 90 deg with 300 to 450 μm steel shot as erodent on iron, copper, and titanium with varying grain sizes. The results indicate that the erosion rate is independent of grain size in iron and copper while it is apparently grain size dependent in titanium. The results are rationalized in terms of the negligible contribution of the Hall-Petch component to the flow stress at large strains in the case of copper and iron. The decreasing erosion rate in titanium with increasing grain size was due to the increased interstitial content picked up during thermal treatment and consequent increase in strain hardening and strain rate hardening and not due to increased grain size per se. Adiabatic shear bands were observed in coarse-grained iron under actual erosion conditions. © 1991 The Minerals, Metals and Materials Society, and ASM International.