Echocardiography is entering a critical stage in its development. For many years the technic was considered only an interesting curiosity. However, recently the clinical usefulness of echocardiography has increased tremendously. Many new diagnostic applications, together with the prospect of obtaining direct anatomic and physiologic information in a noninvasive manner, have stimulated great enthusiasm for the technic. Unfortunately, this enthusiasm and general acceptance are creating some problems. First of all, echocardiography has frequently been described as being "simple." This statement is extremely misleading. The examination may produce no discomfort or hazard to the patient; however, one must remember that an improper . . .