Patients are divided into three groups: (1) asymptomatic patients with or without persistent generalized lymphadenopathy (PGL) syndrome; (2) patients with AIDS; and (3) patients who have or have had mild to moderate signs or symptoms consistent with HIV infection. Patients are then randomly chosen to receive one of three different foscarnet doses. The drug is given for 4 weeks, by 1-hour infusion administered every 8 hours. In addition, those patients who are clinically stable and have not experienced severe toxicity at the end of the 4 weeks may continue treatment, in the form of a single daily dose of foscarnet to be administered 5 days per week. Blood samples are taken during treatment and at the first, fourth, and eighth week after treatment. If the patient is on maintenance, blood samples are taken weekly. Effective 7-17-89, patients entering the study are assigned to the lowest foscarnet dose. Patients receive daily treatment for 28 days. Patients who are clinically stable without severe toxicity at 4 weeks have the option of maintenance therapy with foscarnet.