THE EVALUATION WAS BEGUN IN 1974 AND INVOLVED THE LARGE-SCALE SURVEY OF CALIFORNIA DIVERSION PROJECTS TO OBTAIN BASIC DESCRIPTIVE INFORMATION ON PROGRAMS' OPERATION, CLIENTS, AND SERVICES OFFERED AND INTENSE INVESTIGATION OF 15 PROJECTS WITH YEARLY GRANTS RANGING FROM $20,000 TO $250,000. THIS REPORT FOCUSES ON THESE INDIVIDUAL CASE STUDIES AND THE DATA GATHERED IN ONSITE VISITS AND RECORD SEARCHES. FINDINGS REVEAL THAT 51 PERCENT OF ALL CLIENTS SERVED BY THE PROJECTS WERE DIVERTED FROM INITIAL OR FURTHER PROCESSING WITHIN THE TRADITIONAL JUSTICE SYSTEM AND THAT THE 49 PERCENT OF PERSONS WHO WOULD NOT HAVE BEEN PROCESSED WITHIN THE TRADITIONAL JUSTICE SYSTEM WERE REFERRALS--YOUTH WHO CAME TO THE DIVERSION PROJECT VIA A SCHOOL, PARENT, OR SELF. RECIDIVISM WAS STUDIED BY MEANS OF QUASI-EXPERIMENTAL DESIGNS AND INDIVIDUAL RECORD SEARCHES ON 1,345 CLIENTS AND 1,192 CONTROLS. ON A 6-MONTH FOLLOWUP FROM POINT OF ARREST, 25.4 PERCENT OF THE CLIENTS AND 30.7 PERCENT OF THE CONTROLS WERE ARRESTED. ALTHOUGH RECIDIVISM WAS NOT EQUALLY REDUCED FOR ALL TYPES OF YOUTH, IT WAS REDUCED SIGNIFICANTLY FOR CLIENTS WHO HAD ONE PRIOR ARREST. THE AVERAGE YEARLY EXPENDITURES FOR DIVERSION PROJECTS WAS $101,957 AND THE AVERAGE NUMBER OF CLIENTS SERVED WAS 408. THE AVERAGE COST PER CASE FOR ALL CLIENTS WAS $250. THERE WAS AN AVERAGE SAVINGS OF $30.95 FOR EACH CLIENT REFERRED FROM A JUSTICE SYSTEM SOURCE AND A SLIGHTLY SMALLER COST FOR YOUTHS REFERRED BY EXTERNAL SOURCES. IT IS SUGGESTED THAT DIVERSION MIGHT OPTIMALLY TAKE PLACE ON THE OCCASION OF A YOUTH'S SECOND OFFENSE (CERTAINLY NO LATER THAN THE THIRD). NO SINGLE TYPE OF 'BEST' DIVERSIONARY PROGRAM WAS DETERMINED. STUDY DATA AND REFERENCES ARE PROVIDED. (DAG)