A review. Current models of aggressive behavior in animals are described. They include aggression due to social isolation; territorial aggression in pair "intruder-resident"; aggression elicited by direct electrical stimulation of the brain; maternal aggression; learned aggression and genetic models. The models are analyzed comparatively and their application to human aggression is discussed. Effects of different compounds on aggression are considered and involvement of some neurotransmitters and hormones in aggressive behavior is discussed.