We compared arrest onset and frequency and types of charges between a statewide cohort of adolescent girls in the public mental health system and girls of the same age in the general population to investigate important differences that could have policy or intervention implications. Girls in the public mental health system were arrested at earlier ages more frequently and were charged with more serious offenses than were girls in the general population. Our results strongly argue for cooperation between the public mental health and justice systems to provide mental health and offender rehabilitation in their shared population.