Analyses were conducted on a sample of juvenile offenders (n=4,146) who were committed to the California Youth Authority (CYA) in 1964 and 1965, with a 20-year follow-up of arrest data. Results were based primarily on the 2,263 offenders for whom completed information was obtained on the variables included in the analyses. The variables pertained to history of drug and alcohol use, family environment, cognitive ability, antisocial tendencies, early onset of delinquency and age upon leaving school, and life-course-persistent offending. Data were collected through self-report questionnaires, case-worker interviews, and official records. As part of the assessment processes, offenders were tested individually and in groups. Results suggested that an adverse family environment was related to the timing and frequency of juvenile delinquency. Cognitive ability, early involvement with alcohol, early age at first arrest, and the number of early arrests were all significant predictors of chronic criminal offending after ages 21, 25, and even after age 31. The timing of first arrest was found to be one of the most important variables for the prediction of chronic criminal activity. 3 tables and 53 references