Statistics indicate that 20 to 30 percent of nonclinical female populations have engaged in or been victims of sexual aggression. Conflicting data exist, however, regarding motivational variables in sexual aggression. Data suggest that male sexual aggressors are a heterogeneous population and that there is no single etiology of sexually agressive behavior. Sexual arousal is emphasized as a major motivational factor in several seminal theories of sexual aggression. The theories are first divided into stimulus and response control models and then further divided into state and trait models. The implication is that different models may apply to different men when they are sexually aggressive. A biosocial perspective of feminist, social learning, and evolutionary theories of rape is presented. This approach is more comprehensive than existing sociobiological theories which primarily emphasize evolutionary components. Several critical components that determine sexually aggressive behavior are identified including the amount and meaning of aggression to the aggressor, lifestyle impulsivity and antisocial personality traits, social competence, the presence and nature of an intrusive offense-related fantasy life, sadism, cognitive factors that include irrational attitudes and distortions, control and dominance needs, and the presence of disinhibitors. The need for a unified theoretical model is emphasized in which the heterogeneity of sexual aggressors is accounted for by the prominence of potential etiological factors. Four variables are identified as motivational precursors to sexual aggression: physiological sexual arousal, cognitions that justify sexual aggression, affective dyscontrol, and personality problems. An effort is made to develop a parsimonious model that encompasses primary causes of sexual aggression against women. Relevant causal variables in this model include tactics of manipulation, abusive home environments, association with delinquent peers, attitudes supporting violence, sexual acting out, and hostility toward women. References, tables, and figures