State-of-the-art electronic monitoring technology requires offenders to wear hypoallergenic, radio frequency transmitters attached to their body, typically on the ankle. These devices provide wireless communication to a base station (receiver) located in the offender's home. The base station is connected to a surveillance center computer, usually via telephone. The surveillance system uses proximity detection techniques (detection of signal presence when the range is less than 70 meters) to monitor when the offender is at home, when the offender leaves the home, and when the offender returns home. Information about offender movement can be recorded and reported to the appropriate law enforcement officials. Electronic monitoring is especially viable because most prisons and jails operate above their intended capacity and prison overcrowding has reached crisis proportions. A comprehensive electronic monitoring system has the potential of providing an alternative to imprisonment while ensuring community safety. Judges can place offenders on electronically monitored probation and pretrial release with the assurance that an electronic monitoring system will detect violations of court-imposed home detention or probation rules. Further, offender awareness of continuous monitoring may reduce the number of release condition violations. Electronic monitoring enables the close monitoring of offenders on mandatory probation, intensive supervision, parole, and pretrial supervision. The potential of electronic monitoring is made possible through new technologies that combine advances in large-scale integrated circuits, communications, real-time computer systems, and software. A program funded by the National Institute of Justice to assess the technological feasibility of electronic monitoring in Pittsburgh is detailed that demonstrates the technical feasibility of locating and tracking a simulated body-worn transmitter in an urban environment using a multicellular system of base station receivers. Additional information on the technical performance of electronic monitoring is appended. 13 footnotes, 14 tables, and 31 figures