We studied the effect of the fungal pathogen Entomophaga maimaiga on gypsy moth (L.) (Lepidoptera: Lymantriidae) populations at three sites on the Monongahela National Forest (MNF) in West Virginia in 2003. Gypsy moth has been established on the MNF since at least 1990, and each of our study sites were located in an area defoliated by the gypsy moth in the year prior to this study. E. maimaiga is a fungal pathogen of the gypsy moth, and epizootics can lead to substantial gypsy moth mortality. We placed laboratory-reared gypsy moth larvae on soil collected from each site and measured consequent rates of infection from E. maimaiga. We also collected resident larvae from the sites and surveyed them for the presence of E. maimaiga. Infection rates of laboratory reared larvae ranged from 11-29 %. In first and second instars, and third and forth instars, infection rates in field collected larvae ranged from14-20% and 25-100%, respectively. We were also unable to detect pupae in concurrent surveys at each site. Despite the lack of pupae, and substantial mortality of gypsy moth larvae due to E. maimaiga, we still observed appreciable levels of defoliation in our study sites and in the surrounding areas.