Human cytomegalovirus (HCMV) retinitis is the most common ocular opportunistic infection in immunocompromised patients and AIDS. It often leads to blindness if left untreated. The question as to how HCMV infection causes retinal pathogenesis and visual destruction in AIDS patients remains unresolved. To answer the question, by using terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling assay, we detected the significant signals of apoptotic cells at the same sites in the HCMV-infected retina of AIDS patients as compared to AIDS patients without HCMV retinitis. In vitro study also revealed apoptosis induced by HCMV infection in human retinal pigment epithelium cells, mediated by activation of caspase 3 and poly(ADP-ribose) polymerase pathway. These results strongly suggest the fundamental role of HCMV-induced apoptosis in mediating cell death in infected human retina and retinal pigment epithelium cells to make severe visual impairment.