Statistical analysis of test results obtained by crushing SiC and ZrO2 yielded the optimum design characteristics for a miniature jaw crusher. The device was needed to reduce subcritical amounts of plutonium ceramics to sizes suitable for reactor use. Tests were conducted with a prototype jaw crusher in which crushing speed, jaw clearance, jaw angle, ratio of feed size to jaw clearance, and feed rate could be varied. A crusher built with the optimum design characteristics crushed (U, Pu)O2 to the particle-size distribution that was predicted and desired.