Study participants were 118 adult male sex offenders who were assessed at a penitentiary in Quebec, Canada. This was part of a larger study of the recidivism of sexual offenders that focused on all sex offenders starting a Federal prison sentence for a sexual offense between 1994 and 2000 in the Province of Quebec. The 118 offenders selected for the current study had all sexually assaulted an adult female (16 years old or older). To measure sexual interests, participants' penile circumference was measured under exposure to audiotapes that described the following scenarios: mutually consenting sexual relationship; rape with physical violence; rape with humiliation; nonsexual physical aggression; and nonsexual, nonaggressive control. Dichotomous situational variables involved in the study were the use of alcohol, the use of drugs, the use of pornography, and a negative emotional state. The level of force exhibited during the sexual assault was measured with a scale developed by Avery-Clark and Laws (1984). The findings showed links between sexual interests, situational factors, and rapists' modus operandi. Offenders with a greater sexual interest in nonsexual violence manifested a higher level of organization in the modus operandi. Alcohol consumption prior to the offense was related to a higher level of coercion; and a negative emotional state prior to the crime was related to a high level of injury inflicted on the victim. Although the authors conclude that the modus operandi of the offenders was related to their personal attributes, this is a dynamic interaction that may fluctuate under situational factors. Suggestions are offered for future research. 5 tables and 54 references