Longitudinal birth cohort data (birth years 1942, 1949, and 1955) spanning 35 years (up to 1974-1976) from Racine, Wis., were used in analyses. Controls for sex, race, age at police contact residence, and present and cumulative offense seriousness were included. Results show that very few youth began delinquent behavior at an early age and continued into adult crime: two-thirds of the males in the three birth cohorts desisted after their fifth criminal justice system contact; and an even greater proportion ceased to have felony-related contacts by that time. Further, neither sanction severity nor number of judicial interventions had consistent effects on future offense seriousness or the decision to desist from future offending. The younger the cohort member at any given police contact level, the less likely that contact would be lasting. Further, for felony-level offenses, the earlier and more severe the sanction, the more likely was future felony-level contact with police in the next 2 years. Being referred to juvenile court or some other agency was a further step in the process of becoming known to the criminal justice system and a forerunner of additional police contacts of an increasingly serious nature. Appendixes provide additional research materials and information. Figures, tables, and 58 references. (Author abstract modified)