Duplex Doppler ultrasound was used to examine 50 breast lesions in 45 patients. Examination was confined to the region of interest, which in most cases was a palpable lump, and the corresponding area of the contralateral breast as a control. In only one patient was a Doppler signal obtained from a normal breast. Nine of the 50 lesions were believed to represent simple breast cysts at sonography and were not treated further. The remaining 41 lesions were excised; 22 were carcinomas and 19 benign (fibrocystic disease 7, fibroadenomas 5, miscellaneous 7). Doppler signals were obtained in 20 of the carcinomas and three of the benign lesions. In this series, the sensitivity of duplex Doppler ultrasound for the detection of breast carcinoma was 91%, and the specificity 89%. The positive predictive value was 87% and the negative predictive value 93%.