Microcysts of the iris pigment epithelium have been described in association with diabetes mellitus, systemic mucopolysaccharidoses. Menkes's syndrome, and in neonates. Our study covers 68 cases obtained at necropsy. We specifically examined the iris pigment epithelium for vacuolation. We found that microcysts are more widespread than previously thought. In our series 57.3% of the cases reviewed by the light microscope showed microcysts. Of interest was the relationship of malignant neoplasm to iris pigment epithelium microcyst: 69.4% of cases with malignancy showed microcyst, whereas only 30% of the cases without neoplasms showed microcysts. Patients treated with exogenous steroid also had a raised incidence of microcysts.