To determine whether cidofovir (HPMPC) therapy administered by intravenous infusion can extend the time to progression of peripheral cytomegalovirus (CMV) retinitis in AIDS patients. To evaluate the safety and tolerance of HPMPC therapy when administered by intravenous infusion in AIDS patients with CMV retinitis that is not immediately sight-threatening. To evaluate the virologic effects of intravenous HPMPC therapy on CMV shedding in urine, blood, and/or semen. To evaluate the impact of HPMPC therapy on visual acuity.