This study aimed to clarify the role of lens epithelium in the mechanism of cataractogenesis. One hundred and twenty-six flat preparations of human lens epithelium obtained by endocapsular cataract extraction were studied. The mean lens epithelial cell density (LECD) was 3,683 +/- 655 cells/mm2; there was no significant difference with respect to age and sex (p > 0.05). A marked reduction in LECD, 2,857 cells/mm2, was noted in patients with advanced cataracts. The differences in LECD among the pure cortical, nuclear, and posterior subcapsular types of cataract were statistically insignificant (p > 0.05). We believe that a vicious cycle existed between the compromised lens epithelium and the formation of senile cataract: as a cataractous lens develops to a particular degree, the lens epithelium begins to lose its cell mass progressively and this results in the decreasing LECD. Simultaneously, the diminishing lens epithelial cell population leads to further cataract formation. Based on the outcome of this study, the authors stress the importance of the status of the lens epithelium in the formation of senile cataracts.