The aim of this study was to determine the efficacy and toxicity of combination cisplatin and etoposide chemotherapy in patients with metastatic carcinoma of unknown primary. Patients were treated with cisplatin (100 mg/m2 iv day 1) followed by etoposide (100 mg/m2 iv days 1-3) every 3 weeks for a maximum of 6 cycles. Patients with progressive disease after two or four courses could receive FAC (fluorouracil, doxorubicin, and cyclophosphamide) until progression. Twenty-five patients were entered and were assessable for response and toxicity. Fifteen (60%) patients had adenocarcinomas. Patients received a median of four courses. Toxicity was mainly hematologic including grade III/IV neutropenia. The overall response rate was 32%. There was no complete response, 32% partial responses, 32% stable disease, and 36% disease progression. Median response duration was 4 months (range: 2-5 months). The median overall survival of the 25 patients was 8 months. No objective response could be obtained with FAC, but 33% of patients achieved stabilization of the disease for at least 3 months. This cisplatin-etoposide combination demonstrated some activity against an usually resistant disease.