Age-related changes in the lenses of 90 Wistar male rats, whose ages ranged from 7 to 26 months, were studied morphologically and morphometrically. Morphological studies were performed using biomicroscopy, light microscopy, scanning electron microscopy and transmission electron microscopy. Early cataract formation was observed biomicroscopically in rats of 19 months of age and the number of cataractous lenses increased with aging. Age-related morphological changes in the lenses were observed before cataract formation and these histological changes showed various forms with aging. Flat preparations of the lens epithelium were examined with a computer-assisted cell-analyzer. The mean cell density decreased and the mean cell area enlarged in both central and germinative zones of the lens epithelium with aging. These results suggest that age-related changes of lens epithelial cells do occur and may be associated with the formation of Wistar rat cataract.