Examines the Dollard et al. (1939) frustration-aggression hypothesis. The original formulation's main proposition is limited to interference with an expected attainment of a desired goal on hostile (emotional) aggression. Although some studies have yielded negative results, others support the core proposition. Frustrations can create aggressive inclinations even when they are not arbitrary or aimed at the subject personally. Interpretations and attributions can be understood partly in terms of the original analysis but they can also influence the unpleasantness of the thwarting. A proposed revision of the 1939 model holds that frustrations generate aggressive inclinations to the degree that they arouse negative affect. Evidence regarding the aggressive consequences of aversive events is reviewed, and Berkowitz's cognitive-neoassociationistic model is summarized.