During the past several years, the production of high resolution images of organs in intact animals and human beings using nuclear magnetic resonance (nmr) has generated much interest and raised the possibility that the technique could be usefully applied to clinical problems. Because the images are derived from biochemical as well as structural information, valuable data relating to the metabolic status of the tissues and organs may be obtained. Furthermore, nuclear magnetic resonance imaging involves no potentially hazardous ionizing radiation. The technology of the technique is complex and much work remains to be done defining the biochemical and physiologic basis of such images, but the potential rewards of defining the metabolic state of organs such as heart and brain in the intact animal and human justify continued research.