In order to estimate the therapeutic activity and tolerability of immunochemotherapy with recombinant interferon-alpha 2b (rIFN-alpha 2b) plus dacarbazine (DTIC), a study was carried out in 61 patients with cytologically and/or histologically confirmed metastatic malignant melanoma. The treatment regimen was as follows: rIFN-alpha 2b 2 x 10(6) IU intramuscularly on days 1 to 4, and DTIC 800 mg/m(2) intravenously on day 5, repeated at 3-week intervals until the progression of the disease or, in the case of a complete response, for up to 6 months, The overall response rate was 28%-12% complete response (CR) and 16% partial response (PR). The median response duration was 10.9 months (CR 11.5 months, PR 9.3 months; P > 0.05). Responses occurred in soft tissue and lung metastases only. The median times to treatment failure for responding and non-responding patients were 10.9 and 3 months, respectively (P < 0.0001), and the median survival durations were 16.5 and 5.8 months, respectively (P < 0.0001). The stratification of the patients into a low-risk group (World Health Organization performance status [WHO PS] less than or equal to 1 and soft tissue or lung metastases) and a high-risk group (WHO PS = 2 or disease localization other than skin, lymph nodes or lung) showed a significant advantage for the first group with respect to the response rate, median time to treatment failure and survival duration. A flu-like syndrome was recorded in 72% of patients, nausea and vomiting in 34%, haematological toxicity in 26%, hepatic toxicity in 5%, and neurotoxicity in 5%. In view of the results obtained in our study and those reported in the literature, IFN plus DTIC immunochemotherapy represents a reasonable treatment option, particularly for patients with soft tissue and lung metastases.