As with society at large, violence in psychiatric settings is a serious clinical problem. Despite a great deal of attention, however, very little is currently known about the underlying theory or interventions to reduce aggression and violence in hospital settings. In this study, some psychiatric patients were viewed as having a general, aggressive, interactional style, motivated by the traits of Intimidation and Interpersonal Control, which when combined were labeled Coercion. A causal model in which violence and aggression were hypothesized to be predicted by a coercive interpersonal style and negatively predicted by an accommodating interpersonal style was tested. These interpersonal styles were proposed to mediate antecedent variables, that is, history of violence, psychiatric diagnoses, and length of hospitalization. Data were collected in two hospitals on psychiatric patients (N = 156) and analyzed using multiple regression techniques. The results of theoretical model testing suggested that 60% of the variance in Aggression was explained by four model variables: (a) Intimidation and Interpersonal Control (Coercion) (beta = .44), (b) Length of Hospitalization (beta = .26), (c) History of Violence (beta = .27), and (d) Bipolar Affective Syndrome (beta = .21). The implications for clinical care are discussed.