San Diego County was one of eight California counties that received funding from the State for the ROPP. ROPP has targeted first-time probationers 15 1/2 years old and younger who evidence risk factors for becoming serious, chronic offenders. The ROPP evaluation for all participating counties consisted of randomly assigning all eligible juveniles to ROPP (treatment group) or to standard probation (comparison group). These groups were then compared on the following outcomes: number, content, and disposition of subsequent petitions to declare the juvenile a ward of the juvenile court; number of days served in any local or State correctional facilities; number of days of school attendance during the current or most recent semester; and grade-point average for the most recently completed school semester. For each of these outcomes, the groups were compared at 6-, 12-, 18- and 24-month intervals from intake. Between May 1997 and December 2001, 196 cases were assigned to the San Diego County ROPP treatment group and 171 to the comparison group. The process evaluation included facilitating program replication by documenting implementation, as well as collecting qualitative information that would place the findings of the impact evaluation in context. The results of the impact evaluation showed variable results in anticipated outcomes. Although the ROPP sample did not have fewer filed or sustained petitions, ROPP participants were more likely than the comparison group to receive probation violations, which suggests the increased level of accountability that accompanied increased supervision. Other outcome measures were also positive in at least one of the four reassessment periods. Among the most effective ROPP features were the maintenance of a small client-to-staff ratio, having centrally located services, using graduated sanctions and immediate responses, providing intensive alcohol and drug-related treatment services, and having an onsite court school. Program features that were ineffective were including youth who would have been better served through programs that focus on specific risk factors and relying upon services outside the target community. Problems encountered included the lack of parental support for program efforts, the lack of continued collaboration and communication among and within agencies, and limited space for staff and clients. Future plans are described, and recommendations are offered for other counties that might pursue a ROPP. 2 tables, 25 figures, 2 references, and appended ROPP sample and comparison group descriptives, statistical significance test results, and data collection instruments