Gemcitabine is a commonly used chemotherapy for biliary tree carcinomas, achieving response rates of 10% to 60%. Preclinical studies indicate that fixed dose rate infusion optimizes accumulation of gemcitabine triphosphate and may enhance the clinical activity of gemcitabine. We conducted a phase II study of fixed dose rate gemcitabine in 15 chemotherapy-naive patients with advanced cholangiocarcinoma and gallbladder carcinoma. Gemcitabine was administered at a dose of 1500 mg/m2 over 150 minutes weekly for 3 weeks every 28 days. Fourteen patients were evaluable for response. No complete or partial responses were observed. Two patients (13%) had stable disease lasting a median of 9 weeks. The median time to progression was 9 weeks; median survival was 20 weeks. There was considerable grade 3/4 hematologic toxicity, including neutropenia in 49% of patients, leukopenia in 40%, anemia in 27%, and thrombocytopenia in 27%. Grade 3/4 nonhematologic toxicities were minimal. We conclude that fixed dose rate gemcitabine results in significant myelosuppression and has minimal activity in patients with biliary tree carcinoma.