Fifty patients suffering from histologically proven metastatic melanoma were treated with a combination of DTIC (400 mg/m2 i.v. every 28 days) and recombinant alpha 2A interferon (Roferon-A) 10 x 10(6) U/m2 daily, administered intramuscularly or subcutaneously for 2 months followed by 7 x 10(6) U/m2 3 times a week. Treatment was carried out for a period of 12 months unless progressive disease was noted after 3 months. Among the 49 evaluable patients, 6 achieved a complete response (CR) and 4 a partial response (PR) (response rate, 20%) at 2 months, 8 CR and 3 PR (25%) and 8 CR and 2 PR (23%; 95% confidence limits, 13-40%) occurred at month 6 and 12 respectively These responses occurred notably in patients with cutaneous (3 cases) or lymph node metastases (4 cases), but 3 responses included visceral sites: lung (1 CR), liver (1CR and 1PR). Average response duration was 16.5 months (range 4-29 + months). The time required for objective response can be up to 6 months, which suggest that treatment should receive a reasonable trial period (at least 3 months). Clinical toxicity consisted mainly of a flu-like syndrome, anorexia and fever, and occurred in more than 50% of patients; hematologic and hepatic toxicities required a dose reduction in 54% of patients but in only one case did treatment have to be terminated because of this. Seventeen (35%) of the patients are still alive, 4 with metastases (follow-up period: 18-34 + months) and 13 without metastases (follow-up period: 13-32 + months). A combined regimen of r-IFN alpha 2A and dacarbazine is effective in treating patients with metastatic melanoma, with acceptable toxicities and a reasonable quality of life (out-patient treatment or district nurse care). The objective response rate (23% at 12 months) compares favourably with those of earlier trials using the same combination of drugs, and occurred not only in cutaneous and lymph node metastases but also in visceral metastases.