The youth service bureaus were established by the California legislature in 1968. Methods used for the evaluation included designing and maintaining an information system on youths served, obtaining service area delinquency statistics, observing programs, interviewing project staff and community resource people, and providing technical assistance to bureaus conducting supplementary evaluations. Findings indicated that the bureaus' main characteristic was the development and direct provision of services to youths referred by a variety of agency and individual sources. From July 1971 to June 1972, 10 of the bureaus provided direct service to almost 5,000 new clients, who were referred for both delinquent and nondelinquent reasons. New clients were most often 15 years old, and family counseling was the most common service delivered to clients. Data from selected bureaus indicated that youths referred to the bureaus were less likely to be arrested in the 6 months after bureau intake than in the 6 months before intake. Juvenile arrests decreased in a majority of the bureau service areas when compared with the period before the bureaus were opened. In addition, the number of juvenile arrests referred to probation intake dropped from 20 percent to 40 percent in four of the five areas for which data were available. Although justice agencies in service areas did not refer all of the diverted youth to the bureaus, the presence of a bureau appeared to influence their handling of youths in trouble. Overall, the bureaus were instrumental in diverting youth out of the justice system and appear to have reduced delinquency in their service areas. Descriptions of the bureaus' organization and services, tables, and extensive appendixes presenting forms as well as descriptions and assessments of each of the pilot youth services bureaus, are provided. Reference notes and a bibliography listing 48 references are also included. (Author abstract modified)