<qa>  What is the mainstay of chemotherapeutic agents for gastrointestinal malignancies?5-FU has been the mainstay of chemotherapeutic agents for gastrointestinal malignancies. The use of weekly 24-hour infusion of HDFL produces high clinical response in a variety of cancers, including colorectal, gastric and breast cancers, with minimal chemotherapy-related toxicity. Gemcitabine is a synthesized deoxycytidine analogue that is metabolized to dFdCTP in tumor cells and results in inhibition of DNA synthesis and depletion of normal cellular nucleotide pool. It has been shown to be active in the treatment of pancreatic cancer and non-small cell lung cancer. Since the biliary tract and the pancreas share a common embryonic origin and cancers from both sites are characterized by resistance to most chemotherapeutic agents, we postulate that gemcitabine may also be effective for cancer of the biliary tract. In our institution we have devised a regimen of weekly gemcitabine and 24-hour infusion of HDFL for patients with advanced or metastatic pancreatic adenocarcinoma. In 18 evaluable patients, 2 achieved a partial response and 3 minor response. The median duration of response was 4 months and the treatment-related toxicity was acceptable. 