Background: Irinotecan and cisplatin with concurrent radiotherapy is a powerful treatment combination for patients with limited-disease small-cell lung cancer (LD-SCLC). The objective was to determine the dose-limiting toxicity (DLT) and maximum-tolerated dose (MTD) of irinotecan and cisplatin with concurrent thoracic radiotherapy (TRT) as a once-every-three-weeks schedule. Patients and methods: Patients with LD-SCLC received a fixed-dose of irinotecan (340 mg) and cisplatin (135 mg) at day 1 in cycles 1 and 4. During cycles 2 and 3, irinotecan and cisplatin were given in a dose-escalation schedule with concurrent TRT (once daily, total dose 45Gray). Results: No DLT was observed at first two levels (irinotecan 100mg or 120mg and cisplatin 100mg at day 1 of cycles 2 and 3). In the first five patients, four episodes of grade III diarrhoea/dehydration were observed at cycles 1 and 4. Therefore, from the sixth patient on, fixed-dose irinotecan at cycles 1 and 4 was reduced to 250mg. At the subsequent level of irinotecan 140mg and cisplatin 100mg in cycles 2 and 3, two DLTs (severe oesophagitis and late vertebral. radiation toxicity) were observed in one patient. Conclusion: Irinotecan 140mg and cisplatin 100mg with concurrent TRT was considered the MTD. Irinotecan and cisplatin in a once-every-three-weeks schedule is not recommended due to severe toxicity. Irinotecan may be more suited for intermittent weekly administration. (c) 2007 Elsevier Ireland Ltd. All rights reserved.