9-Aminocamptothecin (9-AC) is a water-insoluble camptothecin derivative that demonstrated broad activity in pre-clinical studies. In vitro, greater anti-tumor efficacy can be achieved with prolonged administration. A minor response was observed in gastric cancer in a phase I study. We conducted a phase II study of 9-AC in 15 patients with previously untreated metastatic gastric cancer and adenocarcinoma of the gastroesophageal junction. 9-AC was administered at a dose of 25 microg/m(2)/h over 120 hours (3000 microg/m(2) over 5 days) on two consecutive weeks every 21 days. Fourteen patients were evaluable for response. There were no objective responses. Three patients had stable disease lasting a median of 3.4 months (range 1.6-4.3 months). Median time to progression was 1.4 months; median survival was 5.2 months. Grade 3 neutropenia developed in 20% of patients, and anemia in 7%. Grade 3 nausea and fatigue each developed in 7% of patients. We conclude that 9-AC given by 120-hour continuous infusion demonstrates no clinical activity in patients with metastatic gastric cancer.