The utility and ultimate role of positron emission computed tomography in health care delivery is difficult to assess at present and needs to be defined in the future. It would seem that with improvements in instrumentation and physiologic indicators, and with the development of compact, reliable, and generator-like cyclotrons, "physiologic tomography" will become more widely applicable. Physiologic tomography of the heart undoubtedly represents an important new tool for investigative studies that will improve our understanding of cardiac physiology in health and disease. The quantiative aspects as well as simultaneous evaluation of more than one segment of myocardial performance, e.g., simultaneous study of mechanical function, blood flow, and metabolism and their interdependency, will provide new insights into myocardial physiology. Because many of the cardiovascular disorders may originate at the cellular or metabolic level, it is hoped that this technique will serve as a means for the early detection of cardiac disease, perhaps at a stage when it is still amenable to therapy.