Shock‐tube experiments have been conducted to study the nonequilibrium gas‐surface interaction which occurs when a thick shock wave in argon reflects from a coplanar, heat‐conducting wall. Fast‐response instrumentation (rise time≲ 0.1 &mgr;sec) was used to monitor variations in temperature and normal stress on the surface of the shock‐tube end wall during and immediately following reflection of the incident shock wave. The laboratory observations are compared with computer predictions obtained by Deiwert using the direct‐simulation Monte Carlo method, and excellent agreement is obtained when a suitable average thermal accommodation coefficient is chosen for the wall surface. In the present case, with the wall surface probably covered with adsorbed gases, best agreement between laboratory and simulation results is found for an accommodation coefficient of 0.75.