The study concluded that the effect of the zero-tolerance juvenile drunk driving legislation in Pennsylvania was an 80-percent increase in juvenile drunk-driving arrests. Juvenile drunk-driving arrest rates per 100,000 licensed juvenile drivers increased from a monthly preintervention average of 41.6 to a postintervention average of 75. Prior to the legislation, approximately 201 juveniles were being arrested monthly in Pennsylvania for drunk driving; after the legislation, the monthly average increased to 359. Further, despite the strong significant increase in juvenile drunk-driving arrest rates, there was no significant impact on monthly juvenile driver fatality rates. A similar pattern was found for Ohio's juvenile zero-tolerance drunk driving law. This research supports the observations made by Paternoster (1987) that "perceptions of the certainty and severity of punishment do not seem to deter trivial and infrequent behaviors of high school and university students." Numerous dependent variables were used in examining the impact of Pennsylvania's zero-tolerance juvenile drunk driving law. The variables were juvenile drunk-driving arrest rates in Pennsylvania and Ohio; adult drunk-driving rates of arrest in Pennsylvania; juvenile alcohol-related arrests other than drunk driving in Pennsylvania; and juvenile alcohol and nonalcohol-related fatality traffic accident rates in the two States. All of the variables were measured from January 1990 through December 2003, with the exception of Ohio's juvenile drunk-driving arrest rates. The data for this variable were not available prior to June 1993. The research used an interrupted time-series design in evaluating the effectiveness of Pennsylvania's law. 9 tables, 12 figures, approximately 110 references, and appended supplementary information on types of effects measured, newspaper media search, and the fatality analysis reporting system