Purpose: To compare the power Doppler ultrasonographic (PDUS) findings of angiogenesis occurring in solid breast with the histopathologic findings. Materials and Methods: Thirty-one cases of pathologically proven solid breast lesions (eight benign, 23 malignant) were retrospectively reviewed, focusing on tumor size (< 3 cm, $geq$ 3 cm), the amount (none, mild,marked), morphology (none/linear, branching, disordered) and pattern (none/peripheral, central, penetrating), as demonstrated by power Doppler ultrasonography. We compared the PDUS findings with microscopic micro-vessel density (Max-MVD, the number of micro-vessels revealed at pathologic examination after factor - VIII staining). Statistical significance was determined using the x2-test. Results: Max-MVD tended to increase according to fumor size, but the relationship was not statistically significant. In solid breast lesions there was close correlation between the observed increase in the intensity of Doppler signals and increased Max-MVD (P < 0.05). Morphologically, branching and disordered vessels were more often seen in malignant lesions, though the relationship between this finding and increased Max-MVD was not statistically significant. Penetrating and central Doppler signals were more frequent in malignant lesions and showed close correlation with increased Max-MVD (P < 0.05). Conclusion: The increased intensity of Doppler signals and the central and penetrating pattern of solid breast lesions seen at power Doppler sonography were closely related with increases in Max-MVD.