This data collection was designed to assess the effects of the New York Juvenile Offender Law on the rate of violent crime committed by juveniles. The data were collected to estimate the deterrent effects of the law and to permit the use of an interrupted time-series model to gauge the effects of intervention. The deterrent effects of the law are assessed on five types of violent offenses over a post-intervention period of 75 months using two comparison time series to control for temporal and geographical characteristics. One time series pertains to the monthly juvenile arrests of 16- to 19-year-olds in New York City, and the other covers monthly arrests of juveniles aged 13 to 15 years in Philadelphia, Pennsylvania, the control jurisdiction. Included in the collection are variables concerning the monthly rates of violent juvenile arrests for homicide, rape, assault, arson, and robbery for the two juvenile cohorts. These time series data were compiled from records of individual police jurisdictions that reported monthly arrests to the Uniform Crime Reporting Division of the Federal Bureau of Investigation.