Endorphins are a collection of opioid-like neurochemicals scattered throughout the nervous system which have profound effects upon the neurohormonal regulatory mechanisms of the brain-stem and all that it controls. Endorphins, primarily beta-endorphin, are elevated with exercise, which places athletic activity in a pivotal role to modulate--usually by inhibition--diverse physiologic functions. They are important in the adaptative process of humans, and models of endorphinergic effects are presented which help to relate their role from the intra-cellular to the macro-function. Explanations and some speculations are offered concerning other non-athletic manipulations of endorphins and how they may be used in sports. Some hazards to athletic performance may be related to endorphinergic effects. Somewhat like their exogenous counterpart (morphine), endorphins may be part of an endogenous euphoric reward system, and as such would reinforce behavior conductive to the perpetuation of their elevation.