ABSTRACT. The Monte Carlo method was applied to an impact model to investigate the impact of polydisperse microparticles with surfaces. The Monte Carlo results were compared to experiments. Two different situations were examined: the normal (90 ± ) impact of microspheres with a molecularly-smooth silicon surface, and the oblique (< 90 ± ) impact of microspheres with a Formica surface. In the former, the percentage of microspheres captured by the surface and the overall capture velocity distribution were determined given the statistical distribution of the microsphere diameters. In the latter, both the Formica surface roughness angles and the diameters of the microspheres were treated as statistical variables. The mean values of the Monte Carlo simulation of the coef cient of restitution and the impulse ratio were found to agree with the data at the 95% con dence level. Finally, this approach was applied to model the impact of Lycopodium spores with a Formica surface.