According to the National Comprehensive Cancer Network (NCCN) clinical practice guideline for gastric cancer (2006, the first edition), 5-FU/Leucovorin (LV), 5-FU-based, cisplatin (CDDP)-based, oxaliplatin (L-OHP)-based, taxane-based, and irinotecan (CPT-11)-based, ECF are recommended. We used modified FOLFOX 6 (mFOLFOX 6) for pretreatment, that is oxaliplatin-based chemotherapy, for a patient who had received 5-FU-based, CDDPbased, taxane-based, and CPT-11-based treatment for an unresectable gastric cancer case responding to mFOLFOX 6. A 73-year-old male admitted to our hospital for treatment of advanced gastric cancer was diagnosed to be inoperable. A combination chemotherapy docetaxel and CDDP and S-1 as first-line treatment, CPT-11 and CDDP as second-line treatment, weekly paclitaxel treatment as third-line treatment, and MTX and 5-FU as fourth-line treatment were performed. He had progressed after 5-FU-based, CDDP-based, taxane-based, and CPT-11-based chemotherapy. There are no effective approved drugs for gastric cancer in Japan. Oxaliplatin was reportedly effective for metastatic gastric cancer, but it is still non-approved in Japan. After receiving an explanation of oxaliplatin-based therapy, he gave informed consent. Oxaliplatin-based therapy for this patient was then evaluated and approved under an institutional review board of Higashi Sapporo Hospital. mFOLFOX 6 used for the oxaliplatin-based therapy. After 2 courses of mFOLFOX 6, he showed a partial response. Oxaliplatin-based treatment was thought to be promising for previously CDDP-treated patients with unresectable gastric cancers.