A regimen of sequential chemoimmunotherapy (SCIT) was studied in a phase I/II study to analyze toxicity, anti-tumor and immunomodulatory effects in patients with previously untreated metastatic cutaneous melanoma. Treatment consisted of dacarbazine (DTIC) 800 mg/m2 administered intravenously (i.v.) on day 1, followed by subcutaneous (s.c.) molgramostim (GM-CSF), 10 times 2.5 micro g/kg on days 2 to 12, s.c. low-dose interleukin-2 (IL-2), 10 times 1.8 MU on days 8 to 18, and s.c. interferon-alpha-2b (IFN-alpha), 5 times 6 MU on days 15 to 20. Dosages were not escalated. Therapy was given in the form of outpatient treatment. Changes in T-lymphocyte phenotype and in soluble mediators were monitored during treatment. A total of 32 patients with stage IV melanoma were enrolled in the study. Treatment was well tolerated, without serious toxicity. In all cases, it could be given as outpatient treatment. Ten subjects out of the 31 patients evaluated showed an objective response, with 4 complete responses (CR) and 6 partial responses (PR); the response rate amounted to 32% (95% CI: 16-49%). Median survival of all patients was 8 months, with those patients who responded to treatment living longer than the non-responding group. Survival rate at 1 year was 22%. Monitoring of the effects of treatment revealed increased numbers of activated T-lymphocytes, both in the CD4 and in the CD8 subsets. The levels of soluble mediators such as sIL-2R and sCD8 were also increased. Changes were noted as early as the GM-CSF treatment period, and were observed to a further extent during IL-2 treatment. In the present study, it was found that this sequential chemoimmunotherapy regimen consisting of 4 agents (DTIC, GM-CSF, IL-2, IFN-alpha) has acceptable toxicity, can be administered on an outpatient basis, results in increased numbers of activated T-lymphocytes, and induces activity against metastatic melanoma that warrants further investigation.