In 1996, an infusion of more than $20 million in State and Federal money was committed to San Francisco's development of an array of new prevention and diversion programs that targeted first-time and nonviolent juvenile offenders. These programs included home-based supervision and day treatment services for first-time or minor offenders. One of the central elements of the reform was the establishment of a new, decentralized intake system to assess and refer juveniles to community-based services so as to reduce unnecessary detention. The new services focused on a significant reduction in San Francisco's historical reliance on custodial detention, so as to make available resources for community-based programs. In order to examine the impact of the reforms on juvenile detention, this study analyzed juvenile detention trends in San Francisco over the past 15 years. The study found that the population at the Youth Guidance Center was at historically high levels despite 5 years of unprecedented investment in new programs and a decline in the juvenile population and felony and misdemeanor arrests. Based on these findings, there is no evidence that new prevention and diversion programs resulted in a lower juvenile detention population. Further, a disproportionate number of minority juveniles were housed in detention. In the course of the implementation of the reforms, a wider pool of lower risk juveniles were absorbed into the system in order to keep the juvenile hall population and the rolls of new programs filled. The new programs became adjuncts to current operations rather than replacing the core system elements. This study demonstrates that reform measures must be accompanied by screening mechanisms that ensure new programs and services target higher risk institutionalized juveniles. The targeting and expansion of services to first-time and minor offenders had no effect on reducing detention populations. 8 tables, 5 figures, and 15 references