To assess the response rate and the tolerance of irinotecan as first-line therapy, 40 patients with metastatic gastric cancer received irinotecan 350 mg m(-2) every 3 weeks administered as a 30 min infusion. Among the 35 patients evaluable for response, two complete and five partial responses were recorded (response rate: 20.0% (95% CI:8.4-36.9%)). In total, 16 patients achieved stable disease and 12 progressive disease. In all, 66 percent of the patients benefited from tumour growth control. The median time to progression was 3.0 months (95% CI: 2.3-4.4%). The median overall survival was 7.1 months (95% CI: 5.2-9.0%). The probability of being alive at 6 months and 9 months was 61.0 and 32.4%, respectively. The median number of cycles per patient was 3 (range 1-14), and the relative dose intensity was 0.98. The most common grade 3-4 toxicities by patients were diarrhoea 20%, asthenia 10%, nausea 7.5%, vomiting 5.0%, abdominal pain 5%, neutropenia 38.5%, leucopenia 28.2%, anaemia 12.8% and thrombocytopenia 5.1%. Febrile neutropenia occurred in 12.5% of patients. These findings indicate that irinotecan is active and well tolerated in patients with metastatic gastric adenocarcinoma and warrants further evaluation in this clinical setting.