THE 1971 STUDY ANALYZED BOOK LOSS FROM THE LIBRARY AND RECOMMENDED THE INSTALLATION OF DETECTION HARDWARE WHICH WOULD RESPOND TO ELECTRONICALLY SENSITIVE PIECES INSERTED INTO BOOKS AND OTHER MATERIALS. ALL MATERIALS IN THE REFERENCE AND CIRCULATING COLLECTIONS ACQUIRED SINCE 1974 HAVE SUCH SENSITIVE PIECES. THE COST OF THE DETECTION DEVICES WAS $11,622 AND THE INITIAL COST OF SENSITIVE PIECES WAS $19,986. ANNUAL COSTS HAVE BEEN $7,894 FOR SENSITIVE PIECES AND $523 FOR MAINTENANCE. THE INSTALLATION OF THE PIECES INTO EACH BOOK REPLACES THE PASTING OF BOOKPLATES AND INVOLVES NO ADDITIONAL EXPENSE. TO DETERMINE THE NUMBER OF DOCUMENTS THAT WOULD HAVE BEEN STOLEN HAD THE SYSTEM NOT BEEN INSTALLED, THE 1971 COLLECTION LOSS RATE WAS APPLIED TO THE 1976 ESTIMATE OF THE NUMBER OF DOCUMENTS IN THE COLLECTION. THIS METHOD SUGGESTS THAT 3,154 DOCUMENTS WERE NOT LOST BECAUSE OF THE ELECTRONIC SECURITY SYSTEM. ABOUT 12 PERCENT OF LOST BOOKS WERE ACTUALLY REPLACED. SINCE THE COST OF SEARCHING FOR AND REPLACING A LOST BOOK AVERAGES $22.63, THE LIBRARY SAVED $8,237 IN 1976. A COST-BENEFIT CALCULATION INDICATES THAT THE SYSTEM WILL PAY FOR ITSELF IN 38 MONTHS. TABLES PRESENT LOSS DATA AND COST-BENEFIT DATA. REFERENCES ARE APPENDED. (GLR)