The study of 592 male juvenile offenders is the largest and most detailed study of serious juvenile offending yet conducted in Northern Ireland. The authors tracked the seriousness of individual convictions prior to sentencing to training schools following discharge from open and secure training schools and also longitudinal criminal offending into adulthood. The study found no significant difference between male juvenile offenders sentenced to open training schools in Northern Ireland and those who progress to secure custody and training at Lisnevin in terms of offense seriousness at any stage prior to their placement in training schools. The recidivism rate over 1, 2, and 3 years for those discharged from open training schools was consistently lower than for those discharged from secure custody. Shorter lengths of stay, particularly in open training schools, were associated with lower recidivism rates. For both forms of custody, lower rates of recidivism were associated with juveniles who committed violent crimes or sexual offenses; juvenile offenders most likely to recidivate were those who committed traffic offenses and theft. Eighty-nine percent of the overall sample were reconvicted as adults, aged 18 to 35 years old. As adults, the most striking finding was the increasing proportion (20 percent) convicted of violent crime. The juveniles least likely to reoffend as adults were those who committed violent or sexual offenses as juveniles. Recommendations are offered for juvenile correctional dispositions based on these findings. 7 tables and 38 references