The first use of drug testing in the criminal justice system was as an adjunct to treatment, as an aid in identifying heroin users in need of treatment and then monitoring their progress. Benefits of drug testing as a treatment tool were further recognized in a 1975 White Paper on Drug Abuse. Drug testing in the criminal justice system expanded in the late 1970's and early 1980's as criminal justice officials began using it as a tool to enforce compliance with supervision requirements, including abstinence from drug use. Between 1987 and 1991, the Bureau of Justice Assistance funded five jurisdictions in Arizona, Wisconsin, Oregon, and Maryland to establish pretrial testing drug demonstration projects, and results from these projects were mixed. Pretrial drug testing programs continue to be interested in defendant drug use but do not always use drug testing as a way of identifying and monitoring drug users. Reasons for this are discussed, various drug testing technologies are described, and costs of conducting pretrial drug testing are estimated. Current applications of pretrial drug testing are listed. 25 notes and 2 tables