The field of nitric oxide (NO) research has developed in explosive proportions since the discovery of endogenous NO in 1986. The first biologically important actions of NO were vasodilation and inhibition of blood clotting, by mechanisms involving stimulation of cyclic GMP production. The cyclic GMP system is the principal signal transduction mechanism by which NO elicits many of its physiological effects in mammals. NO acts as a CNS and peripheral neurotransmitter, where NO facilitates memory, learning, recall and erectile function. Based on these properties of NO, new drugs have been and are being developed to treat hypertension, atherosclerosis, stroke, angina pectoris, heart failure, vascular complications of diabetes, GI ulcers, impotency and other vascular disorders. The unique properties of NO allow for the opportunity to develop novel drugs for diagnosis, prevention and treatment of a multitude of cardiovascular and other disorders.