The evaluation found sufficient evidence of program effectiveness to recommend the expanded use of drug testing of arrested youth and the referral of drug-using youth to appropriate services. Arrest referral was most effective for those who were not already involved with substance abuse and other services as well as those who were at an early point in their substance misuse. Arrest referral apparently provided an additional opportunity to increase young offenders' access to treatment services. The youth had been arrested mainly for property crimes such as theft and burglary. Youth who received referrals reported using a range of substances. The most common were cannabis (30 percent), tobacco (30 percent), and alcohol (23 percent). Over half of those who reported using each of these substances did so either daily or weekly. Generally, the process of arrest referral identified and addressed a broad range of issues beyond offending and substance abuse. The pilot programs at 10 sites implemented diagnostic and referral schemes for children and youth (10-17 years old) arrested for various crimes. Drug testing was conducted for 14-17 year-olds. The evaluation encompassed all 10 sites and included stakeholder interviews, interviews with youth, analysis of monitoring data, analysis of Youth Offending Team data in pilot and comparison sites, and analysis of cost data. Data are reported only for the five sites that were involved in all parts of the evaluation; however, recommendations regarding the future of the program are made based on data from all sites. 53 tables, 18 figures, 18 references, and appended methodology