Sodium diethyldithiocarbamate (Imuthiol, DTC) has previously been observed to promote T-cell maturation in animal models and to reduce lymphadenopathy and improve survival in a murine AIDS model. In addition, several clinical studies have suggested that one dosage regimen may be active in patients with HIV infection. We conducted a randomized, controlled dose response study of intravenous DTC in patients with the acquired immunodeficiency syndrome (AIDS) and AIDS-related complex (ARC). Drug associated toxicities included gastrointestinal upset, burning at the infusion site, metallic taste, sneezing, confusional states, hyperactivity, delusional thinking, and myoclonus. Toxicity was ameliorated by dose reduction. The maximally tolerated dose varied for individual patients from 200 mg/m2 weekly to 800 mg/m2 twice weekly. No myelosuppression was observed. In patients with greater than 200 CD4+ cells/uL, a statistically significant reduction of lymphadenopathy occurred; whereas no beneficial effects were observed in patients with less than 200 CD4+ cells/uL. Improvement in symptom score and stabilization of CD4+ count also occurred in the treated group, although these trends did not reach statistical significance. Further controlled clinical trials of DTC in earlier HIV infection are warranted.