Cytomegalovirus (CMV) retinitis is the most common ocular opportunistic infection in patients with the acquired immune deficiency syndrome (AIDS), in whom it may cause loss of vision. The early diagnosis of CMV retinitis depends on patient awareness of often subtle clinical symptoms; screening examinations may be of benefit. Aggressive treatment of the condition is imperative. Ganciclovir administered intravenously has been shown to be effective therapy, but treatment must be continued indefinitely and is associated with a risk of neutropenia. Careful monitoring during treatment is required. Investigational methods of treatment, including intravitreal injection of ganciclovir or use of foscarnet, another antiviral agent, may be of benefit if intravenous ganciclovir therapy must be discontinued.