Twenty-four evaluable patients with metastatic melanoma have been entered in a multicentre Phase II study of two induction cycles of human recombinant interleukin-2 (rIL-2) 18 x 10(6) IU/m2/day continuous i.v. bolus on days 1-5 and days 12-17. Dacarbazine (DTIC) 850 mg/m2 i.v. bolus was given on day 26. The cycle was repeated at five weeks. Maintenance therapy was scheduled three weeks after the completion of the induction treatment, consisting of rIL-2 18 x 10(6) IU/m2/day for five days alternating with DTIC 850 mg/m2 i.v., every three weeks, for a total of 18 weeks. Median age was 44 years (range 23-80), and Karnofsky index was 100 (range 80-100). One patient had received prior chemotherapy with hydroxyurea and one patient had prior radiotherapy. Six patients responded (25%): two had complete responses (CR) and four had partial responses (PR). Stable disease (SD) was seen in five patients. Responses occurred in the following sites: liver 2/9 (22%), lung 3/14 (21%), skin 2/11 (18%), and lymph nodes 3/12 (25%). Duration of CR was 11+ and 13 months. PRs lasted 2, 5, 7, and 11+ months. Of note, time to progression in patients with SD was similar to that of responders: 4, 4, 11+, 11+, and 14+ months. Toxicity included fever, skin rash, fatigue, anorexia, and diarrhoea in most patients. Two patients had a weight gain of more than 10%. Hypotension requiring vasoactive agents or interruption of rIL-2 occurred in four patients, creatinine elevations WHO grade 1-2 in seven patients, and bilirubin elevations WHO grade 1-3 in six patients. One patient developed transient ventricular tachycardia. It appears that rIL-2 and DTIC in this schedule is feasible and effective, but not clearly superior to rIL-2 alone.