A sight-threatening cytomegalovirus (CMV) retinitis is often associated with acquired immune deficiency syndrome (AIDS). We report the detection and quantitation of antibodies specific for CMV and human immunodeficiency virus type 1 (HIV-1) in the vitreous fluid and serum of an AIDS patient suffering from bilateral CMV retinitis. The ratio of the concentrations of HIV-1-specific immunoglobulin G (IgG) to total IgG in the vitreous fluid was found to be higher than that of the peripheral blood, indicating a local production of HIV-1-specific IgG synthesis within the ocular compartment. In contrast, CMV-specific IgG levels in serum were found to be higher than that of vitreous fluid, indicating an intact blood-ocular barrier. CMV and HIV were also isolated from the ocular tissues of this patient. These findings are consistent with the hypothesis that CMV retinitis may be associated with HIV-1 infection of the ocular tissues, which evokes an HIV-1-specific humoral immune response locally within the ocular compartment.