The Southwest Oncology Group has evaluated the activity of cis-dichlorodiammineplatinum(II) at a dose of 75 mg/m2 given as an iv bolus injection every 3 weeks to 25 fully and partially evaluable patients with advanced Hodgkin's disease and non-Hodgkin's lymphoma. One complete response, two partial responses, and one improvement less than a partial response were noted. Myelosuppression, in the form of leukopenia and thrombocytopenia, was identified and seemed to be more prevalent and more severe than in previous studies. We have attributed this to the extensive prior treatments which these patients had received and to the presence of tumor-bearing marrow which was observed in some of them. The anticipated toxic effects which were noted included nausea and vomiting, anorexia, diarrhea, renal injury, and hyperuricemia. The precise role of cis-dichlorodiammineplatinum(II) in the management of human lymphomas awaits elucidation.