The cohort contained 8,483 youths (4,208 males and 4,275 females) born in 1959 and having resided in the county since 1970. Nearly 1 of every 4 males and about 1 of every 10 females were arrested at least once before reaching 18 years-old. Nearly half of those arrested a first time were arrested two or more times. Among males arrested twice, more than 2 of every 3 committed further delinquent acts. The 721 delinquents arrested more than once were responsible for 72.6 percent of all arrests. Arrest rates were higher for youth in lower socioeconomic classes and nonwhite youth. Also, delinquents were more often born outside of Sacramento County and had changed residence more often than nondelinquents. Delinquency occurred more often among those with lower academic grade point averages and those not attending school. Average age at first arrest was 11.6 for males and 11.4 for females. First-time status offenders were just as likely to recidivate as other types of first offenders. Implications from the findings are that intervention services should focus on nonwhites among lower socioeconomic groups and transient families, and schools should develop programs to deal with the needs of those at risk of poor achievement. Further research should determine the factors that distinguish youth who commit delinquent acts and then desist from those who recidivate. The findings from this study are compared with those of a Philadelphia cohort study. (Author summary modified)