Catecholamines play a regulatory role in the cardiovascular system, primarily via beta (1-2)-adrenoreceptors (AR). However, in the late 1980s, the cloning of a third beta-AR subtype (beta 3-AR) in the heart has altered the conventional view on the regulation of heart function via the betaadrenergic receptors. Additionally, in blood vessels, beta 3-AR was shown to produce relaxation. Currently, the physiological role of beta 3-AR is not clearly known. Hence, the purpose of this review is to summarize the physiological evidences supporting the functional roles of beta 3-AR in various tissues, particularly cardiac and vascular. In addition, this review discusses the potential role of beta 3-AR in obesity and insulin resistance and emphasizes their putative involvement as new therapeutic targets.