The therapeutic benefit of adding interferon alpha (IFNalpha) to established single-agent and combination chemotherapy regimens for the treatment of metastatic melanoma has not been proven. We designed the present study to estimate the response rate of IFNalpha, dacarbazine, cisplatin and tamoxifen in patients who had not been treated with systemic therapy for advanced disease. Using a schedule similar to that which had previously been shown to favor IFNalpha plus dacarbazine over dacarbazine alone, we treated patients with an "induction" regimen of IFNalpha, 15 mU m(-2) day(-1) intravenously 5 days/week for 3 weeks. Following induction, schedules of IFNalpha, 5 mU m(-2) day(-1) subcutaneously three times a week, and tamoxifen, 10 mg orally twice a day, were begun. Dacarbazine, 250 mg m(-2) day(-1) and cisplatin 33 mg m(-2) day(-1) for 3 consecutive days were repeated every 4 weeks, and subcutaneous IFNalpha and oral tamoxifen were continued until the discontinuation of chemotherapy. We treated 25 patients (18 men and 7 women, median age 52 years) and observed only 1 objective response (response rate 4%, 95% confidence interval 0.1%-20%). The toxicities of the regimen consisted of moderate myelosuppression and constitutional side-effects. On the basis of the low antitumor activity of this regimen, we do not recommend it for further study or for use as standard therapy of metastatic melanoma.