An open-label randomised comparison of efficacy and tolerability of irinotecan plus high-dose 5-fluorouracil (5-FU) and leucovorin (LV) (ILF) with etoposide plus 5-FU/LV (ELF) in patients with untreated metastatic or locally advanced gastric cancer. One cycle of ILF comprised six once-weekly infusions of irinotecan 80 mg m(-2), LV 500 mg m(-2), 24-h 5-FU 2000 mg m(-2), and ELF comprised three once-daily doses of etoposide 120 mg m(-2), LV 300 mg m(-2), 5-FU 500 mg m(-2). In all, 56 patients received ILF and 58 ELF. Median age was 62 years, Karnofsky performance 90%, and disease status was comparable for both arms. The objective clinical response rates after 14 weeks treatment (primary end point) were 30% for ILF and 17% for ELF (risk ratio (RR) 0.57, 95% confidence interval (CI) 0.29-1.13, P = 0.0766). Overall response rates over the entire treatment period for ILF and ELF were 43 and 24%, respectively (RR 0.56, 95% CI 0.33-0.97; P = 0.0467). For ILF and ELF, respectively, median progression-free survival was 4.5 vs 2.3 months, time to treatment failure was 3.6 vs 2.2 months (P = 0.4542), and overall survival was 10.8 vs 8.3 months (P = 0.2818). Both regimens were well tolerated, the main grade 3/4 toxicities being diarrhoea (18%, ILF) and neutropenia (57%, ELF). The data from this randomised phase II study indicate that ILF provides a better response rate than ELF, and that ILF should be investigated further for the treatment of metastatic gastric cancer.