The monograph presents the theoretical foundations and author's empirical data on the psychology of aggression. The definition of aggression and aggressiveness is formulated. The main theoretical approaches to the understanding of aggression are highlighted, including the evolutionary approach, the psychoanalytic approach, Gestalt-theory and cognitive-behavioral conception. Great attention is paid to the consideration of an aggression act through the framework of the theory of functional systems (P.K.Anokhin). The author of this book proposes to include in the understanding of aggression a proactive view on human behavior. From this position, one can analyze many planned, deliberate aggressive actions, including antisocial behavior. The second part of the monograph presents the results of the study of aggressiveness (and its personality determinants) in people with mental disorders - organic mental disorders, mood disorders, neuroses, and schizophrenia. The book will be useful for general psychologists, clinical psychologists, psychiatrists, criminologists and social workers.