PURPOSE: Integrins are cell surface proteins that anchor the cells to the extra-cellular matrix. It has recently been found that integrins are involved in proliferations, migration, differentiation and survival signal transduction. We studied the expression of integrins in normal and cancer tissue of Korean breast cancer patients, and investigated the relationship between integrin expression and the characteristics of breast cancer. METHODS: Normal and malignant breast tissues were taken from 25 breast cancer patients who were admitted to the Ajou University Hospital. Specimens were immediately preserved in a nitrogen tank at the time of the operation. Total RNA was extracted, and semi-quantitative reverse transcriptase polymerase chain reactions (RT-PCR) performed with PCR primers for integrin alpha1, alpha2, alpha5, and alphav, and integrin beta1, and beta3. The integrin expressions were compared between the normal and malignant tissues, and the expressions were analyzed in relation to tumor characteristics. RESULTS: Integrin alpha1, alpha5, alphav, beta1, and beta3 were significantly over-expressed in breast cancer tissue than in normal tissue. There was no difference in integrin alpha2 expression between the normal and cancer tissues. Integrin beta1 was over-expressed to a greater extent in lower histological grade carcinomas and to a lesser extent in high grade tumors. Hormonal receptor positive tumor tissue had more alphav, alpha5, and beta1 integrin expressions. There was no significant relationship between integrins and tumor size, lymph node meta-stasis, lymphovascular involvement, or c-erb-B2 expression. CONCLUSIONS: Integrins alpha1, alpha5, alphav and beta3 were over- expressed in malignant breast tissue to a greater extent than in normal tissue. However, studies on the localization of integrin expression in cancer tissue, and co-relations of integrin over-expressions, with survival and drug sensitivity, must be followed to evaluate the clinical value of integrin expression.