Diagnostic ultrasound has become a standard tool in the delivery of healthcare. Although some work was carried out at least as early as the 1940s, medical imaging with ultrasound grew from a modest novelty in the early 1970s to become the widely used and still rapidly growing diagnostic modality of today. In this tutorial lecture, the use of ultrasonic imaging will be illustrated with the aid of video tapes and large-screen projection of representative diagnostic studies. Some of the physics and engineering underlying the generation of clinical images will be reviewed at an intuitive, nonmathematical level. Some of the advantages and limitations of ultrasound in comparison with alternative diagnostic modalities will also be highlighted. Specific applications used to diagnose heart disease will provide opportunities to illustrate ultrasonic imaging of the beating heart. Real-time two-dimensional ultrasonic images of the heart with superimposed color encoded visualizations of Doppler-based estimates of blood flow in the cardiac chambers, which have become the standard for the diagnosis and management of most forms of heart disease, will be shown.