Conventional two-dimensional echocardiography is limited in its ability to illustrate complex cardiac structural relationships arid by the need for assumptions about image plane positioning and ventricular geometry when quantitation is performed. Three-dimensional echocardiography, the coupling of cardiac ultrasound images with a system that locates the images in space with reference to an external coordinate system, can address these limitations. Three dimensional systems currently in use have demonstrated the ability to provide unique views of the heart; for example, a “surgeon's view” of the mitral valve from the left atrium. Three-dimensional echocardiography is also proving to be more accurate than conventional two-dimensional echocardiography for the measurement of left ventricular volume, mass, and ejection fraction and shows promise for the measurement of these parameters of right ventricular structure and function. Three-dimensional echocardiography will be increasingly clinically applicable, because it provides new and improved means of noninvasively visualizing and quantitating cardiac structure and function.