Because of the seriousness of sight-threatening CMV retinitis in AIDS patients and a lack of other available treatments for those patients who cannot be treated with ganciclovir (DHPG) (because of its toxic effect on the body's blood-forming cells, because it did not control the disease, or because patient's blood cell or platelet counts are too low to begin with), it is worthwhile to try an immediate trial with foscarnet. AMENDED: ACTG 093 was originally designed as a randomized dose-ranging study of foscarnet maintenance therapy. Patients enrolled between March 17, 1989, and January 1, 1990, received either 60 mg/kg/day or 90/mg/kg day as maintenance therapy following the 2 week induction period. Based on the preliminary results of ACTG 015/915, which studied maintenance doses of foscarnet of 60 mg/kg/day, 90 mg/kg/day and 120 mg/kg/day, the 60-mg/kg/day and 90/mg/kg/day arms of this study have been closed. All patients entering the study beginning January 2, 1990 will receive foscarnet maintenance therapy on a 120/mg/kg/day algorithm following induction.