Type 4 gastric cancer has a poor prognosis compared with other types of advanced gastric cancer because of the high incidence of peritoneal metastasis which causes intestinal obstruction, hydronephrosis, or obstructive jaundice. Surgical treatment is often only palliative, and systematic chemotherapy is considered to be important for long survival. S-1 showed a higher response rate for undifferentiated-type adenocarcinoma, and S-1 alone or its combination regimens demonstrated greater anti-tumor effects and longer survival time for gastric linitis plastica compared with conventional 5-FU regimens in our historical control study (response rate: S-1/non S-1 57.9%/27.9%, p<0.01; MST: S-1/non S-1 402 days/213 days, p<0.01). S-1 regimens may also improve the survival in patients with type 4 gastric cancer in neoadjuvant or adjuvant settings, but further prospective studies are warranted to prove its significance. Paclitaxel also has a high response rate for undifferentiated-type adenocarcinoma, and can be expected to show high efficacy for peritoneal dissemination. Irinotecan should not be administered in case of intestinal obstruction because its toxicity may be increased. However,survival of patients with type 4 gastric cancer may improve with the availability of active agents like S-1, taxanes, irinotecan as reported in colorectal cancer. Therefore,irinotecan should be administered carefully before intestinal obstruction occurs.