The purpose of this study was to assess the effects of laser in situ keratomileusis (LASIK) on the corneal endothelium. In a prospective study, the corneal endothelium of 87 eyes (45 patients) was examined before and 1 month after LASIK. Patients were divided into two groups: people who wear contact lenses (48 eyes) and people who had never worn contact lenses (39 eyes). The corneal endothelium was analyzed for cell density, percentage of hexagonal cells, and coefficient of variation (CV) of cell size. The mean cell density and percentage of hexagonal cells was significantly higher 1 month after LASIK for all 87 eyes. However, the mean CV of cell size was not significantly different. In contact lens wearers, there was a significant increase in mean cell density and percentage of hexagonal cells, but there was no significant change in mean CV of cell size after LASIK. Among patients who had never worn contact lenses, no significant changes were noted in mean cell density, percentage of hexagonal cells, or mean CV of cell size. In this study, LASIK caused no damage to the corneal endothelium. Postoperative improvements in the mean cell density and percentage of hexagonal cells in patients who were contact lens wearers may be related to the discontinuance of contact lens use after LASIK.