Advent of Doppler echocardiography has provided a great number of informations regarding the intracardiac blood flows. However, conventional pulsed Doppler echocardiography using fast Fourier transform is cumbersome and time-consuming for intracardiac flow imaging despite the capability of localizing the sample volumes in the two-dimensional echocardiograms. Recently, real-time two-dimensional Doppler echocardiography (color flow mapping) has come into clinical practice and made a breakthrough in the diagnosis of cardiovascular disease. Color flow mapping is divided into two different displays; the one is velocity display and the other power display. In velocity display, the direction and magnitude of the mean flow velocity and the spectrum variance are displayed in color, being superimposed on the two-dimensional images in real-time. The flow toward the transducer is depicted as a red color and away from the transducer as a blue color. The velocity spectrum variance represents the turbulence by adding green to red and blue. Additionally, the magnitude of the velocity is displayed by the brightness of color. In power display, the sum of the squared amplitude of the reflected echo signals from blood cells is depicted as red or blue when the flow is directed or away from the transducer, regardless of the velocity. However, this display lacks the display of velocity spectrum variance. Nevertheless, the merits of this display consists in the capability of describing the slower blood flows in wider areas of enlarged chambers. Furthermore, it may have a lower dependence on the incidence of the ultrasonic beams.(ABSTRACT TRUNCATED AT 250 WORDS)