We performed histological examinations on 75 patients in whom a breast lesion was identified by mammography or clinical examination. We found 35 malignant and 40 benign lesions with an average size of 16 mm. In 57 cases (76%) a lesion was identified preoperatively by the use of ultrasound. Blood flow of sufficient magnitude to be visualized by Colour Coded Doppler was only detectable in 22 cases of which 20 turned out to have a malignant lesion. Thus the detection of blood flow by Colour Coded Doppler in a small breast lesion may be considered as a sign of malignancy. However the absence of such blood flow should not be considered as an indicator of a benign lesion. At the same time we would like to point out that the detection of blood flow is also dependent on technical factors of the equipment used.