Data from the 2000 National Incident-Based Reporting System (NIBRS) show that while males make up about nine out of every 10 adult sexual assault perpetrators, totaling about 26,878 incidents within the reporting period, females account for about one out of 10 perpetrators, totaling about 1,162 incidents. Male sexual assault perpetrators offend against child victims about 25% of the time and predominantly choose female child victims, whereas female perpetrators offend against child victims about 40% of the time and choose child victims of both genders equally. Male perpetrators offend against adolescent victims about 40% of the time, and once again tend to choose female adolescent victims. Female perpetrators offend against adolescent victims a comparable amount of time (about 45%), and for forcible offenses (rape, sodomy, sexual assault with an object, and forcible fondling) choose adolescent victims of both genders equally, while for non-forcible offenses (non-forcible incest and statutory rape) they tend to choose predominantly male victims. Finally, adult male sexual assault perpetrators choose adult victims about 36% of the time while female perpetrators choose adult victims only 16% of the time. Implications for professionals are discussed, including recommendations to aid in correct identification of adult perpetrators and child/adolescent victims of sexual assault. (Contains 5 tables, 3 figures, and 1 note.)