Experimental data on the erosive burning of several composite solid propellants are reported and discussed. The data appear to be best correlated in terms of a reduced mass velocity. At low Mach numbers , th is correlation becomes equivalent to several widely used forms employing linear velocity. It is found that the erosive effect is greater in slow-burning propellants than in fast-burning ones , an observation consistent wi th previously reported data for various double-base propellants. The existence of an apparent "threshold velocity for eros ion" is tentatively a t tributed to the failure of the one-dimensional idealization to represent the true flow condit ions obtaining at the fore end of the grain, but i t is emphasized that more comprehensive studies of the erosive-burning phenomenon will be required in order to resolve the threshold velocity quest ion.