It is necessary to note at very beginning, that up to now a comparative approach to the discussion of the structure and function of synthetic and endogenous beta-adrenergic agonists for biomedical and clinical sciences does not appear to be available in the literature. Maybe, one of the reasons for this lies in the differential relations and constant attention of investigators either to the synthetic beta-adrenergic blockers on one hand or to endogenous beta-adrenergic receptor antagonists (EBARA) on the other. Therefore, the main goal of this article is to attempt to overcome this. It is clear now that there are several common properties and relevant features among synthetic beta-adrenergic receptor blockers, endogenous nonspecific beta-adrenergic antagonists (ENBARA) and relative endogenous specific beta-adrenergic antagonists (RESBARA). They are predominantly related to the reduction of adrenergic influence, namely, beta-adrenergic receptor neurotransmission, and, at an intracellular molecular level, to inhibition of adenylate cyclase and a decrease in cyclic AMP content. Other relevant and individual differences are also available and are also discussed.