A phase II study was conducted to assess the response rate and toxicity profile of the combination of irinotecan (CPT-11, Camptosar) and cisplatin (Platinol) administered weekly to patients with untreated advanced adeno-carcinoma of the stomach or gastroesophageal junction. Patients with histologic proof of adenocarcinoma of the stomach or gastroesophageal junction and with adequate liver, kidney, and bone marrow functions were included. Patients were treated with 65 mg/m2 of irinotecan plus 30 mg/m2 of cisplatin, both administered intravenously 1 day per week for 4 consecutive weeks, followed by a 2-week recovery period. Response rate, time to progression, survival, and toxic effects were analyzed. Thirty-six (95%) of 38 registered patients were assessable for toxicity and response. The median number of 6-week cycles per patient was 2.5 (range: 1 to 7 cycles). Four patients (11%) achieved a complete response and 17 (47%) had a partial response for an overall response rate of 58%. Median time to progression of carcinoma was 24 weeks, and median survival was 9 months (range: 1 to 23+ months). There was one treatment-related death. Major toxic effects included diarrhea, neutropenia, and fatigue. The combination of irinotecan and cisplatin is active against gastric or gastroesophageal adenocarcinoma and should undergo further study. The addition of other active drugs or radiation therapy to this regimen would be of interest.