S-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 is active, as a single agent, for the treatment of gastric (RR 44.6%), colorectal (RR 37.4%), head and neck, breast, non-small cell lung, and pancreatic cancers. In gastric cancer, phase III trials (JCOG 9912) comparing 5-FU alone and CPT-11/CDDP combination are currently underway and these results are awaited. Despite of JCOG 9912 study is ongoing, 80% of patients of AGC are already treated by S-1, because of high RR and convenience use for out-patient basis. P-II studies S-1/CDDP, S-1/CPT-11 and S-1/Docetaxel showed high RR(55-76%) and long MST(12-14M). Furthermore, P-III studies are already conducted S-1 vs. S-1/CDDP and S-1 vs. S-1/CPT-11 in Japan. The aim of this study is to compare S-1/Docetaxel vs. S-1 alone in the patients of AGC. This study is a prospective, multicenter, multinational, non-blinded, randomized phase III study.