PURPOSE: The aim of this trial was to investigate the efficacy and safety of cisplatin (P) and irinotecan (I) (PI) alternating with doxorubicin (A), cyclophosphamide (C) and etoposide (E) (ACE) in patients with extensive-disease small-cell lung cancer (ED-SCLC). PATIENTS AND METHODS: Patients with previously untreated ED-SCLC were enrolled in this trial. In the first, third and fifth cycles, PI (P: 60 mg/m(2) on day 1; I: 60 mg/m(2)/day on days 1, 8 and 15) was administered, whereas ACE (A: 50 mg/m(2) on day 1; C: 750 mg/m(2) on day 1; E 80 mg/m(2)/day on days 1-3) was given in the second, fourth and sixth cycles. Each cycle was repeated every 4 weeks. At the end of six cycles, patients who had obtained a complete response were given prophylactic cranial irradiation. RESULTS: In total, 28 patients were enrolled, of whom 27 were assessable for efficacy and safety. Objective responses, including 4 (15%) complete responses, were observed in 25 patients (93%). Median survival time was 12.9 months. The principal toxicity was myelosuppression; grade 4 neutropenia and thrombocytopenia were observed in 89 and 4%, respectively. Febrile neutropenia occurred in 30% of patients. Diarrhea was mild (grade 3-4; 4%). All toxicities were reversible and there were no treatment-related deaths. The mean percentage of the delivered doses, relative to the projected doses, of PI and ACE were 84.6 and 91.1%, respectively. CONCLUSIONS: These results indicate the PI-ACE regimen to have promising activity against ED-SCLC with moderate toxicities.