Adolescents from 10 high schools (n=1,419; response rate 62 percent) in southwestern Ontario (Canada) completed questionnaires that assessed past maltreatment, current adjustment, and dating violence. Logistic regression was used to compare maltreated and nonmaltreated youths across outcome domains. The study found that one third (n=462) of the school sample reported levels of maltreatment above the cutoff score on the childhood Trauma Questionnaire. Girls with a history of maltreatment had a higher risk of emotional distress compared with girls without such histories (e.g., odds ratios [OR] for anger, depression, anxiety, and posttraumatic stress-related problems were 7.1, 7.2, 9.3, and 9.8, respectively). They were also at greater risk of violent and nonviolent delinquency (OR = 2.7) and carrying concealed weapons (OR =7.1). Boys with histories of maltreatment were 2.5 to 3.5 times as likely to report clinical levels of depression, posttraumatic stress, and overt dissociation as were boys without a maltreatment history. They also had a significantly greater risk of using threatening behaviors (OR = 2.8) or physical abuse (OR = 3.4) against their dating partners. The study concludes that maltreatment is a significant risk factor for adolescent maladjustment and shows a differential pattern for male and female adolescents. 3 tables and 37 references