In an Illinois Cancer Center phase II trial, fludarabine phosphate was administered to a total of 14 patients (9 men, 5 women) with advanced, measurable, gastric adenocarcinoma. Fludarabine phosphate was given as a rapid intravenous (IV) bolus at a starting dose of 20 mg/m2/d for the first 5 days of a 28-day cycle. For subsequent cycles, the dose was escalated in increments of 2 mg/m2/d, provided that no toxicities greater than grade 1 were noted. In cases of grade 3 toxicity, dose reductions of 2 mg/m2/d were required, and patients who experienced grade 4 toxicities were removed from study. Receiving one complete 5-day course of fludarabine phosphate and surviving for 4 weeks on study were required for a patient to be evaluable for response. None of the patients responded to treatment. Although fludarabine phosphate was ineffective against gastric adenocarcinoma in this study, toxicity was acceptable at the 20 mg/m2/d times 5 every 28 days dose and schedule.