This study examined adolescent peer-on-peer sexual assault victimization occurring within and outside school. The sample consisted of 1,086 7th through 12th grade students, with a mean age of 15. Most of the respondents were White (54%) or Black (45%), and approximately half of respondents were female (54%). A modified version of the Sexual Experiences Survey was used to assess opposite sex sexual victimization in 7th through 12th grade students. Rates of peer sexual assault were high, ranging from 26% of high school boys to 51% of high school girls. School was the most common location of peer sexual victimization. Characteristics of assault varied by location, including type of victimization, victims' grade level, relationship to the perpetrator, type of coercion, and how upsetting the assault was. Distinctions between sexual assault occurring in and out of school are conceptualized with literature on developmental changes in heterosexual relationships and aggression.