For a long time it was believed that epitelial cells forming endothelium were a membrane system that permitted gas exchange. In addition, it was understood that as a member of a conduction system, its function was to deliver blood through the human body. In the early eighties, the imponance of this organ in controlling vascular smooth muscle tone was demonstrated, and with it, tissue perfusion. Since then, scientists have tried to clarify the endothelium's task in the hean. Today, there is scientific evidence that connects cardiac endothelium, endocardial and coronary microvascular, with the regulation of cardiac pump function; playing a role as imponant as the one played by cardiac preload, cardiac afterload, coronary perfusion and neurohumoral control. The purpose of this article is to review the physiological implications, based on biochemistry and molecular biology principIes, which have the endothelium in the regulation ofcardiac and vascular dynamics.