The U.S. Office of Juvenile Justice and Delinquency Prevention funded the study to achieve two aims: to develop tracking and sample retention procedures for the longitudinal study of delinquent and high-risk youth, and to track and retain the sample until funding is secured for the longitudinal study. In November 1995, data collection began for a sample of 1,832 youths who were arrested and detained. Extensive mental health service information was collected for this sample. A table shows preliminary DSM-IIIR diagnoses, and another table shows urinalysis results. The aims of the study have been achieved. It has developed effective and efficient procedures for tracking and retaining the sample and for managing the flow of information obtained from the project. The study has also effectively tracked sample subjects and secured funding for the longitudinal study of the youths in the sample. The study has logged over 24,000 contacts with these youths. These contacts include all the daily activities of the tracking operation: mass-mailing and birthday card contacts, business reply cards, phone calls from youth, phone calls to parents and schools, and personal visits to incarcerated youth. The database also contains more than 26,000 acquaintance records. When the researchers submitted their Federal grant application for the longitudinal study, they could locate more than 96.5 percent of the sample; and they located and interviewed all 20 subjects in a feasibility study, except for one who was deceased. This was evidence of the researchers' ability to complete the longitudinal study. This report also discusses implications of this study for the field and directions for future research in the Northwestern Juvenile Project. The aims of the longitudinal study are outlined, followed by a discussion of implications of the study for policy or service programs. 3 tables, a sample birthday card for subjects, and a letter accompanying the summer mailing to subjects