Results from the study on the impact of GPS monitoring on sex offender recidivism rates in California include the following: parolees that did not receive GPS monitoring committed new crimes and had their parole revoked more often than did parolees who were placed in the GPS monitoring group; parolees in the traditional monitoring group were returned to custody at a rate 38 percent higher than the GPS monitoring group; and parolees who were placed in the GPS monitoring group complied with the terms of their parole at higher rates than those parolees who received traditional monitoring. This study had two primary purposes: assess both the cost and the effectiveness of the GPS monitoring program in reducing the criminal behavior of high-risk sex offender parolees; and to assess the programs design and implementation. Data for the study were obtained from the State's data management system as well as from a survey of approximately 1,000 California Department of Corrections and Rehabilitation parole officers. The researchers examined arrest records, parole supervision records, GPS monitoring data, and State cost information, and collected information from the parole officers on the GPS monitoring system, caseloads, program staffing, and screening of high-risk sex offender parolees. The analysis found that while the actual per day costs of the program are higher than traditional monitoring, the program is successful in reducing recidivism rates for high-risk sex offender parolees, thus leading to an overall benefit to the community. A set of recommendations based on the findings are discussed in the article and include reexamining the identification of high-risk sex offenders, monitoring attendance at treatment centers, using graduated sanctions to balance cost and risk, and using a monitoring center to screen alerts. A brief history of GPS monitoring policies in California is included in a sidebar to the article.