Analysis is made of a laser supported detonation wave using Whitham’s rule. TheC+characteristic is developed for absorption of laser energy immediately behind a shock wave. The characteristic is then coupled with the Rankine‐Hugoniot equations relating conditions across the shock. In this way an equation for predicting the transient shock strength is obtained. The result is compared to experiment and to steady state laser supported detonation theory. The result of this comparison is that the derived equation does duplicate the transient response of the experiment and (when allowed to run to steady state) it does agree with many of the characteristics of the steady state theory.