The authors have begun to test a fantasy-based information processing model of repetitive sexually aggressive behavior (Burgess et al., 1986). This paper explores hypothetical biological correlates of the model. The discussion is based in the assumption that fantasy is a cognitive process, i.e., a retrieved memory. The paper hypothesizes that there are marked individual differences in the strength or vividness of sexual fantasies as well as their intrusiveness and reiterativeness; the presence of these two factors will be pronounced in cases of repetitive sexual assault. A fully integrated theoretical model must address three questions: What coexisting conditions motivate the offense? What antecedent factors are associated with these conditions? and what constitutional and situational factors increase or decrease the likelihood of the occurrence of the behavior? Regarding the first question, the paper argues that the presumptive condition that motivates the offense behavior is an intrusive, sexually deviant fantasy life whose parameters have a biological underpinning. The origin of the deviant fantasies (second question) is hypothesized to be protracted experiences of childhood abuse. Mediating or disinhibiting factors that increase or decrease the likelihood of acting on the fantasies (third question) are not discussed in this paper. 69 references