Case 1: The patient underwent gastrojejunostomy [T4 (pancreas), N2, P0, CY0] in April 2004, and then 23 courses of chemotherapy with S-1 + DOC (40 mg/m2/day 1:3 w). Then, the regimen was switched to CPT-11 because of a decreased efficacy of the treatment, and CPT-11 was continued for 10 courses. (The patient was alive for 36 months). Case 2: The patient was treated with S-1 [T4 (pancreas), N3, P0, CY0] after surgical bypass in November 2004. After two courses of chemotherapy with S-1, 9 courses of the second-line chemotherapy with PTX (120 mg/m2/day 1:3 w) were provided. As the disease progressed, 15 courses of CPT-11 (125 mg/m2/day 1: 2 w) were administered (The patient was alive for 29 months). Case 3: The patient was diagnosed as CY1 by staging laparoscopy in August 2005. The second-look laparoscopy revealed CY0 after 5 courses of S-1 + PTX (120 mg/m2/day1: 3 w). Although the second-look laparoscopy revealed CYO, gastrojejunostomy was performed because of P1 and T4 (pancreas). Chemotherapy with S-1 + PTX was continued for 18 courses, followed by OPT-11 (The patient was alive for 20 months). This report describes three cases of gastric cancer treated with S-1 based chemotherapy after surgical bypass, which resulted in the long-term survival and an improvement of the patients' quality of life.