Between January 1982 and December 1986, among the 750 patients with the acquired immunodeficiency syndrome (AIDS) who were treated at two adjacent hospitals in New York City, 78 (10.4 percent) needed evaluation for renal disorders. Reversible acute renal failure due to nephrotoxic injury, ischemic injury, or both was present in 23 patients (30 percent) (Group I). The remaining 55 (70 percent) had massive proteinuria, azotemia, or both (AIDS-associated nephropathy; Group II), and irreversible uremia developed in 43. In an additional 18 patients, all of whom had a history of intravenous narcotic drug use, AIDS was diagnosed after the initiation of maintenance hemodialysis for chronic renal failure (Group III). Survival for more than six months after the onset of chronic uremia occurred in only two subjects in Group II; all patients in Group III died within three months of the diagnosis of AIDS. Death in the patients in Groups II and III followed a syndrome of "failure to thrive" characterized by inanition unresponsive to intensive nutritional support and hemodialysis. In contrast, 8 of 17 patients with acute renal failure (Group I) and a serum creatinine concentration above 6 mg per deciliter regained renal function (serum creatinine level, less than 2.0 mg per deciliter). Four of the seven lived for 10 to 24 months, whereas the other four died of sepsis within a month. Our observations suggest that maintenance hemodialysis is not effective in prolonging life either in patients with AIDS-associated nephropathy and uremia or in patients with end-stage renal failure in whom AIDS develops during the course of maintenance dialysis. Hemodialysis may be useful in the management of potentially reversible acute renal failure in patients with AIDS.