Assessment of tissue vascularization with color Doppler (CD) can improve differential diagnosis of tumors. Until now, measurement of flow velocities is restricted to conventional duplex ultrasound of single vessels or semiquantitative scoring of the vessel distribution in CD. We developed a new method for quantification of CD data in organs or tumors by statistical image analysis. Based on standardized image recording, data is acquired from the video output of any ultrasound scanner using a 24-bit color framegrabber in a personal computer. The digitized colors are recognized according to their position in the CD palette bar resulting in an 8-bit color image (number of identified pixels > 99.9%). Within the region of interest, statistics of the detected flow patterns are calculated. The color pixel density and the mean color value varies between recordings of the same image during subsequent systolic peaks with a SD of 10% and 2%, respectively, and within different sections of the same organ or tumor with 25% and 10-50%. This analysis can be used for comparative or longitudinal studies and an objective evaluation of CD in complex vascular formations such as tumors. Its diagnostic impact has already been demonstrated in clinical studies.