The authors investigate the differences between the angiogenesis that occurs in malignant and benign breast tumours (10 specimens of invasive ductal carcinoma and 10 specimens of fibroadenoma) as well as in the adjacent breast stroma of these women highlighting the microvessels by staining their endothelial cells for factor VIII immunohistochemically. The number of vessels counted in invasive ductal carcinoma was significantly higher than the number of vessels counted in fibroadenoma and in the adjacent breast stroma. There was no difference between the number of vessels counted in the fibroadenoma and its adjacent stroma. Even though the patients with invasive ductal carcinoma showed a adjacent stroma with a higher number of vessels, the difference was not significant when compared with the adjacent stroma obtained from patients with fibroadenoma.