The study placed respondents into one of four groups: those youth who were primarily delinquents and not victims (primarily delinquents); those youth who were primarily victims and not delinquents (primarily victims); those who were both delinquents and victims (delinquent-victims); and those who were neither victims nor delinquents. Among boys, the primarily delinquent group composed 20.8 percent of the total sample. Boys who were primarily victims with little or no delinquency composed 17.9 percent of the total sample, and the group categorized as both victimized and delinquent composed 18.1 percent of the sample. Substantial percentages of all three groups were evident throughout the developmental course for boys ages 10-17. Girls had different patterns in both typology groups and age of changes in victimization and delinquency. Except for the girls who were neither victims nor delinquents (52.5 percent), the largest group of girls was the primarily victim group (21.2 percent). The primarily delinquent group (13 percent) and delinquent-victim group (13.3 percent) were smaller than the comparable groups among boys. Among both boys and girls, delinquent-victims tended to experience more life adversities and mental health symptoms than other groups. They also received less social support. Implications are drawn for adolescent development and for intervention by practitioners. The study's methodology is also explained. 2 tables, 3 figures, and 34 references