Integrin-linked kinase (ILK), a serine/threonine protein kinase, implicates in cellular control of cell-matrix interactions and cell proliferation that is associated with a highly invasive phenotype of certain tumors. To study whether ILK is involved in the development and progression of gastric carcinoma, we examined the expression of ILK in gastric carcinoma cell lines, primary gastric carcinomas and corresponding non-neoplastic mucosa using reverse-transcription polymerase chain reaction (RT-PCR) and immunohistochemistry and analyzed the relationship with clinicopathological parameters. The expression of ILK mRNA was detected in 4 of 5 gastric carcinoma cell lines and 22 of 35 (63%) microdissected tumor samples of primary gastric carcinoma using RT-PCR. The incidence of cases with ILK mRNA expression was significantly higher in scirrhous and intermediate type (82%) than in medullary type (44%) (P=0.0204). Significant association was detected between ILK mRNA expression and presence of nodal metastasis (P=0.0388). Immunohistochemically, strong expression of ILK protein (over 50% of tumor cells were positive) was detected in 69% (84/122) of primary gastric carcinomas, whereas no ILK expression was found in non-neoplastic gastric epithelia. Strong expression of ILK protein was significantly associated with scirrhous and intermediate type (P=0.0217), deep invasion of tumor cells in gastric wall (P=0.0006), and presence of nodal metastasis (P=0.0176). These results strongly suggest that ILK may participate not only in stomach carcinogenesis especially of scirrhous and intermediate types but also in invasion and metastasis of gastric carcinoma. ILK might be a novel molecular marker for aggressive gastric cancer.