The therapeutic effects and safety of intravitreal ganciclovir injection were evaluated in 16 acquired immunodeficiency syndrome (AIDS) patients with cytomegalovirus (CMV) retinitis. The induction therapy was done in a total of 23 courses, i.e., in 14 eyes of 10 patients. Active lesions of CMV retinitis were suppressed by 3 to 7 injections over 21 to 42 days after the initiation of the induction therapy. Intravitreal injections once a week for maintenance suppressed the reactivation of the lesions for at least 6 weeks in 9 eyes of 7 patients among 10 eyes of 8 patients. As for the safety of intravitreal ganciclovir injections in the 16 AIDS patients with CMV retinitis, a total of 354 injections were given and two serious complications, that is, endophthalmitis and retinal detachment were observed in one eye each. During the course of intravitreal injection, 3 of 7 patients developed CMV retinitis in the contralateral eye and systemic CMV infections were suspected in 3 of 12 patients. Intravitreal injection of ganciclovir is thought to be effective for the treatment of CMV retinitis in AIDS patients, but careful procedure and examinations are needed.