Identifying the ways in which male and female sex offenders differ is an important but understudied topic. Studies that do exist have been challenged by a reliance on small and select samples. Improving on these limitations, we use the National Incident-Based Reporting System (NIBRS) to compare male and female sex offenders among all 802,150 incidents of sexual assault reported to police across 37 states between 1991 and 2011. Findings indicated some broad similarities between groups, including the most prominent offense location (home), most common victim–offender relationship (acquaintance), and the rarity of injuries or drug abuse during crimes. However, the data also showed several important differences between male and female sexual offenders. Most notably, females offended with male accomplices in more than 30% of their sexual crimes—far more often than occurred among male sexual offenders (2%). Likewise, females offended against a victim of the same sex in nearly half of their crimes, yet this was only true in approximately 10% of male sexual offenses. Implications for future research are discussed.