Background: Breast cancer represents a group of tumors with a tremendous heterogeneity in its behavior, outcome, and response to therapy. Angiogenesis is an important key step in tumor progression. Microvascular density (MVD), a surrogate marker of angiogenesis can be assessed by CD31 immunostaining. This study aims to evaluate CD31 and p53 expressions in breast cancer, and to determine their correlations with some clinico-pathological parameters. Materials and Methods: This study included 54 specimens of invasive duct carcinoma (IDC). CD31 and p53 immunostaining was assessed using avidin-biotin peroxidase method. Results: CD31 staining was observed along the cell membrane of endothelial cells of microvessels in all breast specimens. The median MVD count as assessed by CD31 expression was 66.5 in IDC. MVD as assessed by CD31 increased significantly with increasing tumor size (P<0.04), tumor grade (P<0.01), lymphovascular invasion (P<0.01) and lymph node metastasis (P<0.05) in IDC. There was significant positive correlation between p53 and tumor size (P<0.05), tumor grade (P<0.002), lymphovascular invasion (P<0.02) and lymphocytic infiltration (P<0.03) in IDC. Positive correlation was present between CD31 and p53 in IDC (P<0.000). Conclusion: Up-regulation of angiogenesis as assessed CD31 expression with increasing grade of IDC may reflect that aggressive tumors are more capable of angiogenesis, and suggest that increased angiogenesis is a poor prognostic sign in IDC. CD31 was correlated with p53 that increased with poor prognostic parameters. Thus, measurements of angiogenesis may have utility for estimation of tumor metastatic risk, and might imply for new strategies to improve breast cancer therapy.