This study was conducted to evaluate the efficacy and the tolerability of a four-drug chemotherapy regimen combined with interferon alpha (IFN) in metastatic melanoma. Between March 1991 and August 1993, 55 patients with advanced melanoma were enrolled for the present multicentre phase II study. Forty-nine patients were eligible and evaluable for toxicity; 48 patients were evaluable for response. The treatment schedule consisted of a 5-day regimen of dacarbazine, vincristine, bleomycin and lomustine, plus 6 x 10(6) IU IFN alpha three times weekly subcutaneously for 2 weeks starting on day 8. The cycle was repeated on day 29. Among the 48 assessable patients, 16 objective responses were seen, yielding a response rate of 33% (95% confidence interval 20%-46%). Seven patients achieved a complete response (CR) of a median of 6+ months (range 1+ to 21+ months) and 9 patients achieved a partial response (PR) of a median of 9 months (range 4-13 months). The median overall survival was 12+ months (range 6+ to 23+ months) for the patients with CR and 15+ months (range 8-20 months) for the patients with PR. Even the survival of the 7 patients with stable disease was fairly long (median 12, range 7-17 months), appearing to be significantly longer than the survival of the 25 patients with progressive disease (median 5, range 1-24+ months). The treatment was moderately well tolerated, although all patients experienced some mild form of toxicity, mostly gastrointestinal symptoms, neurotoxicity and haematotoxicity. Grade 3-4 adverse effects were noted in 39% of the patients. No toxic deaths occurred. It can be concluded that the present regimen produces meaningful responses for patients with metastatic melanoma. A randomised study is needed to determine the effect on survival.