This study reports on the effects of having a history of physical and/or sexual abuse on treatment processes and posttreatment abstinence among adolescents (N = 803) in a multisite study of drug treatment outcomes. A history of physical and/or sexual abuse was reported by 59% of the girls and 39% of the boys and was related to being White and having higher levels of comorbidity, exposure to other traumatic events, dependence on alcohol and marijuana, problem recognition, and negative peer or family influence. Abused adolescents had more service needs at treatment admission and there was some variation in treatment processes related to gender and abuse status. Youths with a history of physical abuse had a lower likelihood of posttreatment abstinence, except among those who had better rapport with their counselors. Attention to treatment processes and engagement strategies is crucial for treating youths in drug treatment who have a history of abuse.