Background and Aim: β-catenin is a cell membrane mol-ecule that is essential for cell-cell adhesion of normal epithelia. It is down-regulated in several epithelial tumors and its expression is correlated with tumor cell invasion and metasta-sis. The aim of this study was to evaluate expression status and angiogenic effect of β-catenin in locally aggressive mammary carcinoma. Methods: Formalin-fixed paraffin embedded tissue blocks of 69 of locally infiltrative mammary carcinoma were evaluated for β-catenin and CD31 expression by immunohistochemistry. Correlation of β-catenin expression with invasive potential of the tumors and with CD31 expression was measured sta-tistically. Results: Expression of β-catenin was weak to moderate in most of the investigated cases. There was a steady decline of β-catenin expression through normal mammary tissue, in situ and invasive ductal carcinoma with frequent cytoplasmic re-distribution of the molecule in invasive tumor cells. There was no significant difference of β-catenin expression among different histological subtypes of breast cancer. Down-regulation of β-catenin expression was frequent in large sized and low grade tumors and reduced expression of this molecule was significantly associated with lymphovascular invasion, skin invasion, muscle invasion and lymph node metastasis. There was no significant association of β-catenin expression with microvessel density of the tumor tissue. Conclusions: β-catenin molecule could help early pro-gression of breast carcinoma and its role is likely related to subcellular redistribution rather than expression level of this molecule.