Objective. To assess the role of Doppler sonography when used in conjunction with mammography and gray scale sonography in differentiating solid breast lesions and to find out whether lesion size is a limiting factor for Doppler evaluation. Methods. One hundred twelve lesions 70 malignant and 42 benign) detected with mammography and sonography were prospectively examined with color, power, and pulsed Doppler sonography. Vascularity was analyzed morphologically (vessel location, form, and color tone) and semiquantitatively (by spectral indices) to determine the valuable diagnostic flow characteristics. The lesions were classified by 2 observers as benign or malignant on the basis of each diagnostic technique (namely, 8 combination of mammography and gray scale sonography, presence or absence of blood flow, morphologic flow analysis, and spectral flow analysis). The results were compared with the histologic diagnosis in 105 lesions and with the clinical and radiologic diagnosis after at least 2 years of follow-up in 7 lesions. Results The sensitivity and specificity of the mammography-gray scale sonography combination were 98.6% and 76.2%, respectively. Neither morphologic nor spectral Doppler analysis proved to be successful on its own; however information obtained from investigated morphologic and spectral flow features increased the specificity of mammography and gray scale sonography for lesions 10 mm and smaller (from 88.9% to 100%) and those larger than 10 mm (from 70% to 96.6%). Conclusions. Our data show that Doppler sonography is a beneficial adjunct to mammography and gray scale sonography for solid breast lesions 10 mm and smaller and those larger than 10. mm.