Chemotherapy options for esophagogastric adenocarcinoma remain limited. Irinotecan has demonstrated broad activity in a variety of epithelial malignancies. Forty-six patients with previously untreated, measurable, unresectable, or metastatic esophagogastric adenocarcinoma were enrolled. Patients received irinotecan (125 mg/m2 intravenously over 90 min weekly) for 4 consecutive weeks followed by a 2-week rest. Forty-three patients received at least one treatment and were evaluable for response and toxicity. One complete and five partial responses were observed, for an overall response rate of 14% (95% CI, 4-24%). Median survival for all 43 patients was 6.4 months (95% CI, 4.6-8.2 months). Grade 3 to 4 toxicity included 10 patients (23%) with neutropenia, 13 patients (30%) with late diarrhea, 6 patients (14%) with vomiting, and 6 patients (14%) with fatigue. We conclude that although single-agent irinotecan is an active agent for esophagogastric adenocarcinoma, the schedule utilized in this trial is associated with moderate toxicity. When used as a single-agent, a tri-weekly schedule may be preferable for this patient population.