BACKGROUND The long-term effects of radial keratotomy on the corneal endothelium are not well understood. We evaluated the effects of radial keratotomy on the corneal endothelium on the central and midperipheral corneal endothelium. METHODS Anterior radial keratotomy in 25 eyes was performed and patients were followed for a duration of 4 to 10 years after surgery. Eleven non- contact lens wearing control eyes did not have surgery and were followed for the same period. Morphometric analysis of specular microscopic images was performed with regard to cell density, percent hexagonality, and coefficient of variation. RESULTS Mean corneal endothelial cell loss rates were 0.4% per year in the radial keratotomy group and 0.9% in the untreated control group over the study duration (mean 7 yr). Morphometric analysis of the cells failed to show a significant change in hexagonality and coefficient of variation. Evaluation of the midperipheral corneal cell counts demonstrated a 1% per year cell loss rate. The cell loss rates in radial keratotomy patients followed over this period were consistent with that noted for normal aging (0.5 to 2.5% per year). CONCLUSIONS Radial keratotomy does not cause accelerated endothelial cell loss over 4 to 10 years.