The role of systemic chemotherapy in the treatment of patients with metastatic neuroendocrine tumors is controversial. While combination regimens containing cisplatin and etoposide have activity against more aggressive neuroendocrine tumor variants, such regimens appear to have little efficacy in patients with well-differentiated neuroendocrine tumor subtypes. The combination of irinotecan and cisplatin is active both against small cell lung cancer and in upper gastrointestinal malignancies but has not been prospectively evaluated in patients with metastatic neuroendocrine tumors. We therefore assessed the efficacy of an irinotecan/cisplatin combination in patients with this disease. Eighteen patients with metastatic neuroendocrine tumors (excluding small cell carcinoma) were treated with irinotecan, 65 mg/m2, and cisplatin, 30 mg/m2, administered weekly for 2 of every 3 weeks. Patients were followed for evidence of toxicity, response, and survival. The toxicities associated with this regimen were mild and included myelosuppression, nausea, and diarrhea. Only one radiologic response was observed among four patients with poorly differentiated neuroendocrine tumors. No radiologic responses were observed in 14 patients with well-differentiated tumors. The median overall survival duration of patients treated with this regimen was 11.4 months. We conclude that while the combination of irinotecan and cisplatin may have activity in aggressive neuroendocrine tumor subtypes, this combination is inactive in patients with well-differentiated neuroendocrine tumors.