Digital rectal examination, prostate-specific antigen and transrectal sonography (TRS) are the main diagnostic tools for evaluating men at risk for carcinoma of the prostate (PCa). PCa has a hypoechoic echo pattern via TRS in 60- 85% of cases. Hypoechoic areas are observed, however, in benign prostatic hyperplasia (BPH) as well. For this reason, TRS yields a low specificity and sensitivity in detecting PCa in screening programs. Additional data, independent of the grey scale information available via TRS, can be obtained by using the innovative technology of color Doppler sonography. This imaging modality allows simultaneous real-time sonographic visualization and evaluation of vascular structures. The present study analyzes to what extent the analysis of blood flow perfusion of prostatic parenchyma can provide further information concerning the pathologic alterations occurring in abnormal prostate tissue. Blood flow phenomena were reproducibly demonstrated in the prostate and in the periprostatic tissue with the color-coded Doppler sonography (CD-TRS). 31 patients with the diagnosis of BPH could be separated into two different groups according to the findings with TRS and CD-TRS. In contrast, patients with histologically proven PCa (n = 16) had subjectively increased perfusion rates. Blood flow phenomena were analyzed using computer-calculated resistive index and pulsatility index as evaluations of flow and frequency. A preliminary analysis of the wave-form characteristics shows that flow in the prostate gland is associated with a high resistive index in both PCa and BPH. The mean frequency demonstrated in the pulsatility index appears to be high in PCa, but low in BPH cases. Further studies are needed to verify the described factors' abilities to differentiate prostate tissue as either PCa or BPH.