Explanations involving the etiology of pathological gambling have tended to emphasize psychosocial factors. However, the possibility that psychobiological factors may be important in the development of pathological gambling behavior should not be ruled out. Psychobiological approaches are becoming ever more prominent with the three main lines of research being (a) a search for a physiological disposition and/or underlying biological substrate in pathological gamblers, (b) an examination of the role of arousal in gambling, and (c) speculation about endorphin-related explanations. The data from questionnaires and interviews with fruit machine gamblers suggest that both physiological and cognitive factors (e.g., the psychology of the near-miss) may be important in the explanation of excessive fruit machine gambling. Thus, if a gambler becomes physiologically aroused when he or she wins or nearly wins, it will stimulate further play, here termed the psychobiology of the near-miss.