Gemcitabine is generally considered to constitute first-line therapy for pancreatic cancer. To determine whether the addition of fluorouracil (5-FU) improves on the results from single-agent gemcitabine, the Eastern Cooperative Oncology Group (ECOG) compared gemcitabine plus bolus 5-FU with gemcitabine alone for patients with advanced pancreatic carcinoma. This trial involved patients with biopsy-proven, advanced carcinoma of the pancreas not amenable to surgical resection. Patients were randomized to receive either gemcitabine alone (1,000 mg/m(2)/wk) weekly for 3 weeks of every 4 or to receive gemcitabine (1,000 mg/m(2)/wk) followed by 5-FU (600 mg/m(2)/wk) weekly on the same schedule. The primary end point of the trial was survival, with secondary end points of time to progression and response rate. Of 327 patients enrolled over 18 months, 322 were eligible. Overall, the median survival was 5.4 months for gemcitabine alone and 6.7 months for gemcitabine plus 5-FU (P =.09). Progression-free survival for gemcitabine alone was 2.2 months, compared with 3.4 months for gemcitabine plus 5-FU (P =.022). Objective responses were uncommon and were observed in only 5.6% of patients treated with gemcitabine and 6.9% of patients treated with gemcitabine plus 5-FU. Most toxicities were hematologic or gastrointestinal; no significant differences were noted between the two treatment arms. 5-FU, administered in conjunction with gemcitabine, did not improve the median survival of patients with advanced pancreatic carcinoma compared with single-agent gemcitabine. Further studies with other combinations of gemcitabine and 5-FU are not compelling, and clinical trial resources should address other combinations and novel agents.