We report two cases of gastric carcinoma with successful downstaging using S-1-based chemotherapy followed by surgical resection, which enabled us to confirm the histological effect of chemotherapy. These patients were associated with extensive distant lymph node metastases for which curative resections were unlikely to be performed. We performed anticancer chemotherapy using S-1 with or without concomitant administration of cisplatin in a neoadjuvant setting. After the successful downstaging of these metastatic gastric carcinomas evaluated by imaging analyses, the patients underwent surgical resections. Effect of the chemotherapy was confirmed by the histological analyses. These cases provide further evidence, suggesting that S-1-based chemotherapy enabled downstaging of stage IV gastric carcinoma associated with distant extensive lymph node metastasis and consequently the following possible curative resections. The review of 16 cases of S-1-based chemotherapy followed by surgical resections indicated that, although downstaging may not be expected when N3 lymph node metastases are evident, the S-1-based chemotherapeutic regimens were effective in short cycles for patients in whom potential curative resection is expected. Survival benefit of downstaging followed by surgical resection, however, remains to be further elucidated.