74 breast tumor patients were preoperatively examined by means of colour and pulsed-wave Doppler sonography using the ultrasonic instrument ALT Ultramark 9 HDI with a broad-band linear scanner, 5-10 MHz. The Doppler flow velocity waveforms, from the vessels of the mammary lesion (affected breast) and the corresponding quadrant of the contralateral breast (non-affected breast), respectively, were compared in respect of the four parameters maximal systolic velocity, minimal diastolic velocity, pulsatility index (PI) and resistance index (RI). In 48 cases we succeeded in representing arterial vessels both inside the affected and the contralateral breast. The aim of the study was to examine whether these parameters show a significantly different degree of deviation in correlation with the tumours being either benign or malign. In cases with benign lesions (n = 24) we did not find any significant differences in all the parameters that we examined. In cases with cancer, however (n = 18), a significantly higher systolic velocity was found in the affected breast compared to the contralateral breast, but there were no differences in the other parameters. Although the quantitative Doppler measurements are angle-dependent parameters, the study showed that the maximal velocity in the affected breast compared to the contralateral breast is the most useful parameter in differential diagnosis of breast tumours.