Deformation of a granite, tonalite and limestone in a plane shock wave was compared with triaxial deformation at 0.00001/sec under the constraint of uniaxial strain. For granite and for limestone at moderate pressure, the stress-strain relation was nearly identical in the two tests; strain under these conditions was elastically recoverable. For the limestone at high pressure and for the tonalite at all pressures, volume decreased permanently. This permanent deformation, compared here for shock and slow strain-rate tests, had about the same strain rate dependence as observed typically in fracture of rocks under triaxial conditions.