Nitroglycerin and other organic nitrates have been used for over a century in the treatment of angina pectoris. Millions of patients, throughout the world, have placed nitroglycerin tablets under the tongue and have experienced rapid and dramatic relief from the chest pain that frequently occurs as a manifestation of disease of the coronary arteries. The empirical observation of the safe use of nitrates for tile alleviation of the symptoms of angina have led to their widespread medical acceptance. The use of organic nitrates preceded any knowledge of their mechanism of action or their ultimate metabolic fate. Thus, more simply stated, although sub­ lingual nitrates helped the patients, little was known concerning what these drugs do to the body or what the body does to the drugs. A substantial number of investigators have focused on these questions especially during the last two decades. We now have considerably more insight into the pathways of degradation of organic nitrates and the relationship of the metabolic processes to the biological action of these agents. Similarly, considerable effort has been expended in understanding the mechanism of action of these agents directly on vascular smooth muscle and on cardiac work and performance. Finally, there is a more substantive understanding of the physiology of the coronary circulation as well as the" pathophysiologic manifestations of myocardial disease.