Male sexual aggression against females is an increasingly serious societal problem. Research and clinical interventions in this area primarily are guided by univariate models and complex multivariate models that are population-specific. There exists no unifying theoretical model in which the findings of different researchers have been incorporated (Quinsey & Marshall, 1983), so as to understand the motivational factors unique to various subtypes of perpetrators. Such a model also would have to be sufficiently flexible to account for the various sexually aggressive modes of expression without being unnecessarily complex or simplistic, if it is to be clinically useful. Specifically with respect to sexual aggression against children, a quadripartite model of sexual aggression is proposed that includes physiological sexual arousal, cognitions that justify sexual aggression, affective dyscontrol, and personality problems as motivational precursors that increase the probability of sexually aggressive behavior (Hall & Hirschman, 1990). The relative prominence of these precursors is used to define major subtypes of sexual aggressors. It is hypothesized that cluster analytic procedures will reveal four major subtypes of sexual aggressors against female children with physiological, cognitive, affective, or personality variables as the primary precursors.