Docetaxel plus cisplatin and docetaxel plus irinotecan are active and well-tolerated chemotherapy regimens for advanced non-small-cell lung cancer (NSCLC). A randomised phase II study compared their efficacy and toxicity in 108 patients with stage IIIb/IV NSCLC, who were randomised to receive docetaxel 60 mg m(-2) and cisplatin 80 mg m(-2) on day 1 (DC; n=51), or docetaxel 60 mg m(-2) on day 8 and irinotecan 60 mg m(-2) on day 1 and 8 (DI; n=57) every 3 weeks. Response rates were 37% for DC and 32% for DI patients. Median survival times and 1- and 2-year survival rates were 50 weeks (95% confidence interval: 34-78 weeks), 47 and 25% for DC, and 46 weeks (95% confidence interval: 37-54 weeks), 40 and 18% for DI, respectively. The progression-free survival time was 20 weeks (95% confidence interval: 14-25 weeks) with DC and 18 (95% confidence interval: 12-22 weeks) with DI. Significantly more DI than DC patients had grade 4 leucopenia and neutropenia (P<0.01); more DC patients had grade >/=2 thrombocytopenia (P<0.01). Nausea and vomiting was more pronounced with DC (P<0.01); diarrhoea was more common with DI (P=0.01). Three treatment-related deaths occurred in DC patients. In conclusion, although the DI and DC regimens had different toxicity profiles, there was no significant difference in survival.