This research examines mental health correlates of different victim-perpetrator relationships among adolescent victims of interpersonal violence. A large and nationally representative sample of adolescents (N = 4,023) responded to structured telephone interviews concerning mental health functioning (posttraumatic stress disorder--PTSD, major depressive disorder, substance abuse/dependence, and delinquency). Those reporting histories of sexual (n = 321) and/or physical (n = 688) assault were queried about specific aspects of their assaults, including their relationship with the perpetrator. After controlling for demographic and assault-related risk factors, the victim-perpetrator relationship remained a significant risk factor for mental health problems. Adolescents sexually assaulted by nonstrangers were at increased risk for PTSD; those sexually assaulted by acquaintances or people they did not know well were at increased risk for delinquency. Adolescents who were physically assaulted by a family member were at increased risk for PTSD. Explanations for the findings and the need for consistent assessment methods across related studies are discussed. (Contains 4 tables.)