Lateral stress and shear strength behind the shock front have been measured in three face centered cubic alloys. Results show different behaviors according to microstructure. A hardening response has been shown in pure nickel, while in stainless steel (SS) 304L, hardening has been shown to be minimal. This has been explained in terms of the stacking fault energy effecting the motion and generation of dislocations. In the high stacking fault energy nickel, dislocation motion is comparatively easy, and hence the microstructure consists of dislocation cells, with a pronounced hardening postshock. In SS 304L with its lower stacking fault energy, dislocation motion is more restricted, and hence deformation is dominated by deformation twins. The behavior behind the shock front correlates with the low degree of hardening observed by others during mechanical testing of preshocked samples. The aluminum alloy 6082-T6 also shows a low degree of hardening behind the shock front. This is believed to occur due to the presence of fine intermetallic particles suppressing the formation of dislocation cells but rather forming a random distribution throughout the microstructure. © 2009 Crown Copyright.