Twenty-five assessable patients with metastatic melanoma have been entered in a multicenter phase II study of two induction cycles of human recombinant interleukin-2(IL2), 18 x 10(6) IU/m2/d continuous intravenous (IV) infusion on days 1 to 5 and days 12 to 17. Dacarbazine (DTIC), 850 mg/m2 IV bolus was given on day 26. The cycle was repeated at 5 weeks. Maintenance therapy was scheduled 3 weeks after the completion of induction treatment, consisting of IL2, 18 x 10(6) IU/m2/d for 5 days alternating with DTIC, 850 mg/m2 IV every 3 weeks, for a total of 18 weeks. Six patients responded (24%); two complete and four partial. Stable disease was seen in five patients. None of the six patients with more than two sites of metastases responded. Maximum response was observed in the first 3 months of treatment. Progression-free periods of 6 months and longer were seen in the two complete responders (8 and 17+ months), in two of the four partial responders (7 and 12+ months), and in three of the five patients with stable disease (9+, 15, and 17+ months). Toxicity included fever, skin rash, fatigue, anorexia, and diarrhea in most patients. Two patients had a weight gain of more than 10%. Eight patients needed intensive care for the observation and treatment of a myocardial injury (one patient), ventricular tachycardia (one), hypotension and oliguria (four), and sepsis (two). Sequential treatment with IL2 and DTIC appears to be effective but not clearly better than could be expected of IL2 alone.