Pancreatic cancer is the fifth leading cause of cancer death in the United States. It is difficult to diagnose at its early stage and only 10-20% of patients are candidates for resection with 5-year survival rate of less than 10%. Patients with unresectable pancreatic cancer has a poor prognosis. Gemcitabine, a cytidine analogue, is the standard chemotherapeutic agent for the disease with median survival time(MST) ranging from 6 to 8 months. Phase Ⅲ study showed that combinations with other drugs, such as oxaliplatine or CDDP, did not contribute to survival time. TS-1, a new oral fluoropyrimidine which consists of the 5-FU prodrug tegafur (ftorafur, FT) and two enzyme inhibitors, CDHP (5-chloro-2,4-dihydroxypyridine) and OXO (potassium oxonate), in a molar ratio of 1(FT):0.4 (CDHP):1(OXO), is commercially available since late 90'in Japan. Phase II trials have demonstrated that S-1 was effective as a single agent for treatment of gastric (RR 44.6%), colorectal (RR 37.4%), head and neck, breast, non-small cell lung, and pancreatic cancers(20%). A combination of gemcitabine and TS-1 is found to be effective and promising in phase Ⅱ trial for metastatic pancreatic carcinoma in selected subjects, but the combination therapy has high rate of side effects. This phase Ⅱ randomized controlled study compares efficacy and feasibility of GEM+S-1 with GEM alone in patients with locally advanced and metastatic pancreatic cancer and performance status of 0-2, aiming at patients in rather ordinary clinical settings.