A study was conducted at the Moffitt Undergraduate Library of the University of California at Berkeley to determine the extent and the cost of book losses due to theft and to determine the cost-effectiveness of book security systems. A sample inventory was taken and the theft rate (13.7%) was statistically derived. The rate of loss was translated into a cost figure, projected over time, and compared with the cost of book security systems. It was shown that the cost of installing and operating a security system was far less than the projected cost of book thefts. (EMH)