Combining chemotherapy and immunotherapeutic agents such as interleukin-2 and interferon alpha-2b might improve treatment results in metastatic melanoma (MM) patients compared with chemotherapy alone. This prospective study evaluated the potential efficacy of a biochemotherapy regimen followed by maintenance biotherapy for the treatment of MM. Twenty-two patients with stage IV melanoma were treated for 5 consecutive days with cisplatin at 20 mg/m, vinblastine at 1.6 mg/m, and dacarbazine at 160 mg/m. Pegylated interferon alpha-2b at a dose of 50 microg every week, subcutaneous interleukin-2, 1.8 MIU, and oral 13-cis-retinoic acid (13-cis-RA) at 0.5 mg/kg were given 5 days/week for 3 weeks each month during the period of chemotherapy administration. Maintenance biotherapy was continued in patients who had a complete or partial response or disease stability (clinical benefit) after six courses of biochemotherapy. The primary endpoint was response; secondary endpoints were the evaluation of the immunologic parameters, toxicity, progression-free survival, and overall survival. Twelve patients (54.5%) achieved a response, and seven (31.8%) maintained stable disease for at least 6 months with maintenance biotherapy. The median progression-free survival and overall survival were 23.3 and 45.7 months, respectively. The most important toxicities from chemotherapy were grades 3 and 4 neutropenia and thrombocytopenia in 41 and 18% of patients, respectively, whereas grade 2 autoimmune reactions were observed in 21% of patients after maintenance biotherapy. A prolonged enhancement of immunologic function was observed in the 19 patients treated with maintenance therapy. A regimen of six cycles of biochemotherapy followed by maintenance immunotherapy is well tolerated, and shows significant activity in patients with MM.