Inclusion Criteria:

- Patient who is pathologically confirmed as gastric cancer

- Patient who has received surgery with D2 or more lymph node dissection and whose
final curability of surgical resection is grade A or B

- Patient whose final stage is II (except for T1), IIIA, or IIIB

- Patient without liver, peritoneal and distant metastasis, and who is negative in
peritoneal cytological diagnosis

- Patient whose age at the registration is ranging between 20 and 80 years old

- Patient who has not received any preoperative therapy including radiotherapy,
chemotherapy and immunotherapy

- Patient who has received surgery for gastric cancer within six weeks before the
registration, and is judged to be capable of oral administration

- Patient who has no serious concurrent complications, and satisfies the following
criteria

- White blood cell count: > LLN or > 4,000 /mm3

- Platelet count: > 100,000 /mm3

- Serum total bilirubin: < 1.5 mg/dL

- Serum AST (GOT), ALT (GPT): < 2.5 * ULN

- Serum creatinine: < ULN

- Patient who has received an explanation of this study by assent documents, and has
given written informed consent to participate in this study

Exclusion Criteria:

- Patient with metachronous or synchronous multicancer

- Patient who contraindicates to TS-1

- Patient who requires continuous use of flucytosine, phenytoin or warfarin potassium

- Patient who has experienced serious drug allergy over grade 3 in the past

- Patient with serious complications including paralysis of intestine, ileus,
interstitial pneumonitis, fibroid lung, uncontrollable diabetes mellitus, heart
insufficiency, renal insufficiency or hepatic insufficiency

- Patient with diarrhea (watery stool)

- Patient who is pregnant or in lactation, or wish to become pregnant during this study

- Male patient who intends to make someone pregnant during this study

- Patient with HIV positive

- Patient who is judged to be inappropriate as subject to this study by the principal
investigator or the doctors in charge