OBJECTIVE To estimate the incidence and prevalence of cytomegalovirus retinitis (CMV-R) in late-stage human immunodeficiency virus type 1 disease. METHODS Cohort study. METHODS The Multicenter AIDS Cohort Study, an ongoing 10-year study of human immunodeficiency virus type 1-infected homosexual men with semiannual visits and CD4+ cell testing. METHODS Three hundred sixty-seven human immunodeficiency virus type 1-infected men from the Multicenter AIDS Cohort Study who were receiving zidovudine and Pneumocystis carinii prophylaxis and who had CD4+ cell counts fall below 0.10 x 10(9)/L (100/microL). METHODS Kaplan-Meier-type estimates for various longitudinal quantifications of incidence and prevalence of CMV-R were obtained. RESULTS Among these 367 individuals, cytomegalovirus disease developed in 103, of whom 73 (71%) had ocular complications. At 4 years after the first CD4 cell count ( < 0.10 x 10(9)/L), the probability for these subjects to have (1) remained living without CMV-R was 11%, (2) died without experiencing CMV-R was 66%, (3) experienced CMV-R and be living was 6%, and (4) experienced CMV-R and died was 18%. During these 4 years, there was a 25% chance for the development of CMV-R and, on average, 0.211 person-years of CMV-R morbidity. Among those subjects in whom CMV-R developed, about 19% did have CMV-R before a CD4+ cell count of less than 0.05 x 10(9)/L ( < 50/microL) was observed, and 81% had CMV-R after the CD4+ cell count reached this threshold. CONCLUSIONS These estimates may be relevant to current clinical practice and help in allocating resources and planning for treatment and prophylaxis against cytomegalovirus disease.