Several of the less clearly defined aspects of S. Schachter and J. Singer's (1962) cognition-arousal theory of emotion are clarified, and empirical evidence pertaining to 3 major deductions from the theory is reviewed. It is concluded that only 1 of these deductions, claiming that misattributed arousal from an extraneous source intensifies emotional reactions, is adequately supported by the data. Little support is found for the 2nd hypothesis, that arousal reduction leads to a reduction in the intensity of emotional state. The status of the 3rd hypothesis, that misattribution of emotionally induced arousal to a neutral source results in a reduction of emotionality, is considered equivocal because of plausible alternative interpretations of the pertinent findings. There is no convincing evidence for Schachter and Singer's claim that arousal is a necessary condition for an emotional state, nor for the suggestion that emotional states may result from a labeling of unexplained arousal. It is suggested that the role of arousal in emotion has been overstated and that the available data support at best a rather attenuated version of Schachter's theory—that arousal feedback can have an intensifying effect on emotional states—and that this arousal–emotion relationship is mediated, in part, by causal attributions regarding the source of arousal.(6 p ref)(PsycINFO Database Record (c) 2016 APA, all rights reserved)