We performed intravenous digital subtraction angiography (IV-DSA) in 31 patients with primary invasive breast cancer, and calculated the maximum density of tumor staining from the time-density curve obtained. Specimens resected from the same patients were stained for factor VIII-related antigen/von Willebrand factor (vWF), and the amount of microvessels was calculated by image processing. A significant correlation (correlation coefficient: 0.85) was found between the maximum density of tumor staining and the vascularity determined by staining for vWF, indicating that the maximum density indirectly reflects the vascularity in the tumor.