This paper reports on an empirical study of defense mechanisms in 60 psychiatric inpatients. Eight defenses--compensation, denial, displacement, intellectualization, projection, reaction formation, regression, and repression--were studied in the context of a two-stage model of suicidal and violent behavior. The results showed that use of regression as a defense differentiated suicidal from nonsuicidal patients, and use of displacement differentiated violent from nonviolent patients. Repression tended to turn aggression inward, and projection and denial turned aggression outward.