PURPOSE: To evaluate the usefulness of contrast-enhanced power Doppler ultrasonography (PDUS) in differentiating small benign from small malignant breast lesions. MATERIALS AND METHODS: Thirty-one solid breast lesions (<2 cm in size; 17 benign and 14 malignant) prospectively underwent US and PDUS before and after the injection of contrast agent (SH U 508A). Morphologic analysis involved independent assessment of the findings of US and the patterns of Doppler signals before and after contrast enhancement at PDUS, and sensitivity and specificity were thus evaluated. The diagnostic accuracy of US accompanied by PDUS was also determined before and after contrast enhancement. Hemodynamic analysis involved measurement of the time lapse between contrast injection at PDUS and observed change in Doppler signals. For this, a sonic VIOR computer-assisted program was used and the results were correlated with the pathologic findings. RESULTS: The sensitivities of US before and after contrast enhanced PDUS were 100%, 35.7%, and 57%, with specificities of 47%, 88.2% and 76%, respectively. The diagnostic accuracy of US was 35% with noncontrast PDUS, and 77% before and after contrast enhanced PDUS. The recorded time lapse between contrast injection at PDUS and observed change in Doppler signals did not correlate closely with the pathologic findings. CONCLUSION: In that it improved visualization of the morphology of vascular Doppler signals, microbubble contrast-enhanced PDUS complemented US and PDUS in differentiating between small benign and small malignant breast lesions.