Testing offenders for illegal drug use has been standard practice for nearly ten years in prisons, jails, work furlough programs, and halfway houses. The article discusses several methods used by clinical laboratories and on-site facilities when testing urine to determine drug abuse. The strengths and weaknesses of laboratory testing and on-site drug abuse testing are outlined, along with the legal issues associated with the testing of criminal offenders. Before deciding whether to use laboratory or on-site testing, criminal justice agencies should weigh the objectives of their programs, their testing needs, and their budget limitations.