A total of 48 patients with measurable advanced gastric adenocarcinoma (n = 16) or adenocarcinoma of the exocrine pancreas (n = 32) were prospectively treated with iproplatin at a starting dose of 270 mg/m2 intravenously over 2 hours. The dose was repeated every 28 days, and dose escalations or reductions were made on the basis of toxicity in the preceding course. No patient with gastric carcinoma achieved either a complete or partial response. One partial response and two complete responses were seen with pancreatic adenocarcinoma for an overall response rate of 10%. One patient has remained free of disease for more than 2 years. The major toxicities were granulocytopenia, thrombocytopenia, nausea, vomiting, and diarrhea. All toxicities were reversible upon discontinuation of the drug. On the basis of this trial, we conclude that iproplatin has no substantive activity in advanced gastric or pancreatic carcinomas.