We evaluated the efficacy of chemotherapy using S-1 after gastrojejunostomy for unresectable gastric cancer with pyloric stenosis. We performed gastrojejunostomy to relieve obstruction in 40 patients from 1993 to 2007. After gastrojejunostomy, 15 patients were treated with S-1(S-1 group), 12 patients were treated with another anticancer drug(non S-1 group)and the other 13 patients received no chemotherapy. After informed consent was obtained, S-1(80 mg/m(2)day)and another anticancer drug was administered. The mean period of administered was 16(range 2-56)weeks in the S-1 group. In the non S-1 group, 5-FU was used in 1 patient, 5'-DFUR in 2, UFT in 3, FP chemotherapy in 3, CPT- 11/CDDP chemotherapy in 1, and 5-FU/PTX chemotherapy was conducted in 2 patients. The one-year survival rate was 63% and the median survival time was 394 days in the S-1 group, against 33% and 169 days, respectively, in the non S-1 group. Appetite loss of grade 3 was observed in one(7%)patient with nonhematological toxicity, but no patient suffered grade 3 hematological toxicity. We observed the course of all patients on an outpatient basis. In conclusion, S- 1 administration after gastrojejunostomy appears to be an effective treatment modality for far advanced gastric cancer patients with pyloric stenosis in view of toxicities, antitumor effects and QOL of the patients.