Suramin sodium is a reverse transcriptase inhibitor with in vitro activity against the human immunodeficiency virus (HIV), the causative agent of acquired immunodeficiency syndrome (AIDS). Ninety-eight patients with AIDS manifest as opportunistic infections (n = 38), AIDS with Kaposi's sarcoma (n = 38), AIDS-related complex (n = 20), or AIDS-associated non-Hodgkin's lymphoma (NHL) (n = 2) were treated with suramin sodium at 0.5, 1.0, or 1.5 g/wk for six weeks followed by maintenance therapy with 0.5 or 1.0 g/wk. Of 72 patients who were HIV culture positive before therapy and were assessable for subsequent HIV culture 40% became culture negative during treatment, with no apparent correlation between virus recovery and serum suramin concentration. No immunologic improvement was noted. One complete clinical remission was noted in a patient with Kaposi's sarcoma and stage IV NHL. Seven minor clinical responses were also noted. Toxic reactions were generally reversible, and included fever (78%), rash (48%), malaise (43%), nausea (34%), neurologic symptoms (33%), and vomiting (20%). Suramin-induced neutropenia was noted in 26%, thrombocytopenia in 12%, a serum creatinine level of 180 mumol/L or higher (greater than or equal to 2.1 mg/dL) in 12%, liver dysfunction in 14%, and clinical and/or laboratory evidence of adrenal insufficiency in 23%. Sixteen patients died while receiving suramin or within three weeks of discontinuation of drug therapy due to infection (n = 6), hepatic failure (n = 3), pulmonary Kaposi's sarcoma (n = 2), AIDS encephalitis (n = 2), AIDS-associated NHL (n = 1), iatrogenic hemo-pneumothorax (n = 1), or pulmonary disease of uncertain etiology. Suramin as currently administered cannot be recommended as effective therapy for AIDS.