The chapter first provides an overview of ethology, including a description of the biobehavioral approaches to the study of aggression, with emphasis on levels of organization or analyses involved in an investigation of any problem from an ethological perspective. The intent is to extrapolate general principles and some of the conceptual and methodological lessons of interest and use to a wider professional audience. The author advocates an adherence to modern synthetic theory of evolution so the benefits of a parsimonious theoretical approach to research on aggression can be exploited and undisciplined empiricism avoided. Examples of neural and hormonal mechanisms mediating aggression illustrate approaches to problems of causation. An ethological, functional taxonomy identifies 14 types of aggression, followed by a critical appraisal of the role of animal-ethnological models for research on aggression and violence. The chapter concludes with a discussion of violence prevention by extrapolating hypotheses from animal studies on context, territoriality, proximity, strangeness, and familiarity. 103 references.