Peritoneal dissemination is the major pattern of recurrence in patients with gastric cancer. Among the 1,337 patients with gastric cancer who underwent a curative resection, a multivariate analysis showed that the independent risk factors for the occurrence of peritoneal dissemination were an undifferentiated tissue type and serosal invasion. We focus our attention on 477 patients with undifferentiated type tumor, in which the postoperative prognosis and the pattern of recurrence after curative resection were evaluated with regard to the depth of the cancerous invasion in the gastric wall. Patients with tumors limiting to the subserosal layer had a satisfactory post-operative course, with five-year survival rates of 98.5%, 97.4%, and 82.5% in patients with tumors limiting to the submucosal layer, the muscularis propria and subserosal layer, respectively. In 179 patients with tumors invading to the subserosal layer, however, the five year survival rate was only 48.2%. Seventy-one died of peritoneal dissemination, while 24 and 15 were due to hematogenous and local recurrences, respectively. Only 50 (27.9%) survived over 5 years without any recurrence.