In the process of formulating the quadripartite model, the authors have attempted to reorganize salient components of existing models. They propose that certain physiological, cognitive, affective, and personality precursors increase the probability of sexually aggressive behavior. The absence of any one of these precursors may decrease the likelihood of such behavior, although the intensity of one or more of the precursors may increase the intensity of other precursors and concomitantly increase the likelihood of sexually aggressive behavior. The heterogeneity of sexually aggressive persons is accounted for by physiological sexual arousal, cognitions that justify sexual aggression, affective dyscontrol, and personality problems. Although not a critical component of the quadripartite model, environmental factors may alter the expression of sexual aggression in form, but not in substance, with respect to basic psychological mechanisms. The authors believe that further progress in assessment and treatment research requires a comprehensive yet parsimonious framework to evaluate the relative prominence of various precursors in different sexually agressive populations. 64 references (Author abstract modified)