We show how to extract a statistically significant temporal signature of quantum chaos from the fluorescence decay of mixed molecular states prepared by multimode partially coherent laser pulses, Specifically, the average fluorescence from appropriately prepared molecules is shown to be an incoherently averaged quantity which, aside from radiative damping factors, is linearly related to the transient part of the average survival probability which distinguishes regular from irregular vibrational dynamics. A three step procedure is developed for removing the masking effect of radiative damping, thereby allowing a direct extraction of a dynamical signature of quantum chaos, Simulated fluorescence signals with regular and irregular vibrational dynamics are analyzed to demonstrate the effectiveness of this approach and to motivate experimental studies. (C) 1997 American Institute of Physics.