Electronic monitoring (EM) of offenders has been in use for just over two decades and motives for using it remain diverse. Some agencies that use EM attempt to deliver humane and affordable sanctions while others seek to relieve jail crowding or to avoid the construction of new jails. Nonetheless, all EM programs aim to suppress the criminal behavior of offenders being monitored and its advocates have always hoped EM could be instrumental in reducing long-term recidivism. This review investigates the history of EM and the extent to which EM empirically affects criminal behavior in moderate to high-risk populations. All available recidivism studies that included at least one comparison group between the first impact study in 1986 and 2002 were considered for the review. Although variants such as GPS tracking and continuous testing for alcohol in perspiration have recently emerged, no studies of these technologies were found that met the review’s inclusion criteria. Studies are examined and combined for meta-analysis where appropriate. Given its continued and widespread use and the dearth of reliable information about its effects, the authors conclude that applications of EM as a tool for reducing crime are not supported by existing data. Properly controlled experiments would be required to draw stronger conclusions about the effects of EM.