Background: Periostin is preferentially expressed in periosteum, indicating a potential role in bone formation. Recently, there have been emerging controversies about its role in invasion and metastasis of human malignancies. We attempted to determine the clinicopathological significance of periostin expression in non-small cell lung carcinoma (NSCLC). Methods: Immunohistochemical staining of periostin protein from 91 cases of NSCLCs was performed using tissue microarray blocks. The results were correlated with clinicopathological parameters. Results: Positive reaction to periostin was predominantly noted in the tumor stroma. The strongest reaction presented as a band-like pattern just around the tumor nests. Non-neoplastic lung tissue and most in-situ carcinomas did not show a positive reaction in their stroma. With respect to tumor differentiation, moderate to poor differentiated tumors (47/77) revealed even higher periostin expression than the well-differentiated ones (4/14) (p=0.024). High periostin expression was positively correlated with E-cadherin and p53 expression, but was not related with patient age, sex, tumor type, PCNA index, b-catenin, cyclin D1, pTNM-T, pTNM-N, stage, and patient survival (p>0.05). Conclusion: These results suggest that periostin might play a role during the biological progression of NSCLC, but may not be related to the clinical prognostic parameters.