S-1 (TS-1)-related studies presented at the 74th Japanese Gastric Cancer Congress are reviewed. Of the papers presented at this conference, 35 were related to S-1. In the panel discussion on the therapeutic significance of oral fluoropyrimidines in gastric cancer, 9 papers were related to S-1 (sensitivities to oral fluoropyrimidines, 2 papers; clinical results of treatment with S-1, 5 papers; and combination therapy with S-1, 2 papers). In the general presentations, there were 26 papers on S-1 related-subjects (clinical studies or clinical practice of S-1, 12 papers; case reports, 3 papers; basic studies on animal models of peritoneal metastasis, 2 papers; and combination therapy with S-1, 9 papers). Several studies showed that S-1 was basically as effective against tumors in postmarketing surveillance in clinical practice as in phase II studies at the time of its development, including a report of a patient with complete response to S-1. Some reports suggested the possibility of using S-1 in neoadjuvant chemotherapy and postoperative adjuvant chemotherapy. The usefulness of S-1 in combination chemotherapy was also suggested in several reports. These results indicate that S-1 is a key drug that can be used in first-line treatment of gastric cancer. It will be necessary to accumulate evidence based on data from clinical trials and clinical applications in the future.