The Ganciclovir-Cidofovir CMV Retinitis Trial (GCCRT) is a randomized, multicenter clinical trial. Patients will be assigned to receive one of two regimens: (1) ganciclovir intraocular device plus oral ganciclovir or (2) intravenous cidofovir. The intraocular device will be surgically implanted at baseline and again every 6 to 8 months in eyes with CMV retinitis. Oral ganciclovir is taken at a dose of 1 gram three times daily. Cidofovir will be administered intravenously at 5 mg/kg once weekly for 2 consecutive weeks and once every 2 weeks thereafter. If disease progression occurs in patients receiving cidofovir, patients will be given reinduction therapy, and oral ganciclovir at a dose of 1 gram three times per day will be added to the treatment. If patients assigned to cidofovir are unable to tolerate that regimen, an alternative systemic regimen will be recommended.