Proper clinical use of real-time, two-dimensional echocardiography depends upon three major factors: the clinical questions posed of these imaging devices, the interrelationship of this technique with other imaging techniques and the quality of the ultrasonic image. The Duke experience with this technique has been primarily based on results obtained with a focused, phased array imaging system over the last three years. During this period of time we have observed that high-resolution, cross-sectional ultrasonic images of cardiac structures provide unique diagnostic information that is not possible by any other method. Similarly, this type of information allows the clinician to pose new questions concerning the use of diagnostic ultrasound in patient care. Improvements in image quality that have accompanied the addition of new scan formats and a broad-band transducer have enhanced the clinical reliability of diagnostic information.