In March 1984, under National Institute of Justice sponsorship, the D.C. Pretrial Services Agency (PSA) began gathering drug-use data at the time of arrest. The testing uses the Emit mechanism, a speedy new automated urinalysis device. The D.C. research is testing for five drugs: heroin, amphetamines, methadone, cocaine, and phencyclidine (PCP). To date, about half of the 600 defendants tested have shown use of one or more of these drugs. In the District of Columbia, information on drug use is considered at the pretrial hearing. Drug users who are released receive different forms of supervision during the pretrial period. In the research study, about one-half of those defendants Emit identifies as users are referred to a drug treatment agency. Other drug-using defendants are required to submit to Emit urinalysis surveillance before trial. Analysis of the results of this long-term study should yield dependable measures of rearrest and court appearance rates of drug users on pretrial release, compared to rates of nonusers similarly released. Prior research on drug use and pretrial arrest and failure to appear in court in the District of Columbia is also discussed. Figures are included.