The effects of lost phase coherence on carrier capture by semiconductor quantum wells are simulated using Schro¨dinger Equation Monte Carlo. Results are shown for polar-opticalphonon-induced capture of both electrons and holes, and for both monoenergetic and thermal distributions of incident charge carriers. Results suggest that semiclassical modeling of hole capture may be sufficient, provided that quantum mechanical reflection from the individual heterointerfaces still is taken into account. However, for a quantum well laser optimized to operate at an electron capture resonance, semiclassical calculations blind to the resonance structure would underestimate the capture rate, whileGolden-Rulecalculations, which assume complete phase coherence, could somewhat overestimate it. ©1997 American Institute of Physics.