In the present study, we evaluated the outcome of preoperative treatment with S-1 and CDDP for the treatment of advanced gastric cancer. Fifty-five cases of advanced gastric cancer received pre-operative treatment with S-1 and CDDP. The tumor control rate( PR and CR according to RECIST criteria) was 55%. The clinical response and histological response to the treatment and curative resection were closely related to favorable postoperative survival. We noted that patients who demonstrated CR or PR received S-1 as postoperative treatment, whereas those with SD or PD were more likely to receive paclitaxel as postoperative treatment. Preoperative treatment with S-1 and CDDP was not only an effective initial treatment, but also demonstrated favorable results in a S-1 in vivo sensitivity test.