The phenomenon of tumor angiogenesis is an important aspect of understanding tumor biology. Studies in breast carcinoma have shown microvessel density (MVD) assessed by immunohistochemistry to be of prognostic importance in primary breast cancer. On the other hand, recently developed highly sensitive color-coded Doppler techniques offer a noninvasive method to examine neovascularisation in breast tumors. The purpose of this study was to determine the relationship between Doppler flow parameters and microvessel count assessed by immunohistochemistry. Fifty-three patients with primary breast cancer were examined preoperatively with color-coded Doppler ultrasound. The obtained Doppler frequency spectra were analyzed for peak systolic flow velocity (Vmax). Following surgery, paraffin-embedded microsections were immunohistochemically stained for factor VIII-related antigen. Tumor angiogenesis was assessed by microvessel count under light microscopy. Undifferentiated tumors correlated with high MVD (p=0.009) whereas other clinicopathological parameters were not associated with MVD. Color Doppler signals were detected in 50 out of 53 breast tumors. Evaluation of tumor flow velocity with various clinicopathological parameters showed a significant correlation with tumor size (p=0.0001) and lymph node metastasis (p=0.02). However, there was no significant correlation between MVD and intratumoral blood flow velocity assessed by color-coded Doppler. Our findings showed that Doppler flow measurement did not correlate with the extent of tumor angiogenesis of breast cancer. The present data give circumstantial evidence that microvessel count assessed by immunohistochemistry reflects the microvascular network, whereas tumor vasculature documented by Doppler ultrasound supplies information on the macrovasculature.