The prognosis of advanced gastric cancer remains poor, given the frequent incidence of peritoneal metastasis. beta1-integrin is known to be associated with metastasis, though few reports have addressed the expression of beta1-integrin subunits in gastric cancer at primary and peritoneal lesions from the perspective of individual cases. We studied specimens from primary tumors from 50 patients and from metastatic peritoneal lesions from 27 patients with gastric carcinoma, including specimens from 22 metastatic lesions taken from the same patients whose primary tumors were sampled. Expression of beta1-integrin subunits, alpha2-alpha6beta1 integrins, was studied using an immunohistochemical method. alpha2beta1-integrin was significantly expressed on a larger proportion of tumor cells in peritoneal metastasis (70.4%) than in primary tumors (48%) (p<0.05), though alpha3beta1, alpha4beta1, alpha5beta1 and alpha6beta1-integrins did not demonstrate significant discrepancy. The expression of alpha2beta1-integrin in peritoneal lesions was significantly increased compared with its expression in the primary lesion in the same individual. In contrast, no relationship was found between the expression level of beta1 integrins and clinicopathological parameters. Peritoneal implantation of gastric carcinoma might be closely associated with alpha2beta1-integrin.