Bitter orange (Citrus aurantium) extract and its primary protoalkaloidp-synephrine are used widely in weight loss/weight management and sports performance products. Because of structural similarities, the pharmacological effects ofp-synephrine are widely assumed to be similar to those of ephedrine,m-synephrine (phenylephrine), and endogenous amine neurotransmitters as norepinephrine and epinephrine. However, small structural changes result in the receptor binding characteristics of these amines that are markedly different, providing a plausible explanation for the paucity of adverse effects associated with the wide-spread consumption ofp-synephrine in the form of dietary supplements as well as in variousCitrusfoods and juices. This paper summarizes the adrenoreceptor binding characteristics ofp-synephrine relative tom-synephrine, norepinephrine, and other amines as related to the observed pharmacological effects.