The initial appearance of criminal defendants in Federal district courts is secured in one of two ways. They are arrested and physically taken into court, or they are summoned to court by a written notice. In both cases, a pretrial interview and investigation occurs. Under standards adopted by the Administrative Office of the U.S. Courts, persons on probation or supervised release who are subject to mandatory drug testing are tested when placed on supervision, with a minimum of one scheduled test per month and one unscheduled test per month for the first 90 days. Cases with a special condition of drug treatment are referred to a drug specialist in the probation office. Pretrial service officers are required to complete urine testing prior to a defendant's initial appearance in court and to include results in the pretrial service report. Interim statistical results of the demonstration program in the eight pilot districts indicate that cocaine is the drug of choice among criminal defendants in Federal district courts, that criminal defendants cooperate with court officials in providing urine samples, that drug testing equipment is reliable, that formal challenges to the legality of the pretrial service urine testing program have not surfaced, and that pretrial testing prior to initial court appearance identifies 33 percent of all tested defendants. Implementation of the mandatory drug testing program in Federal judicial districts in New York, Michigan, Texas, Arkansas, North Dakota, Minnesota, Nevada, and Florida is discussed. Drug testing equipment, supplies, and services are described, along with drug screening procedures, logistical issues, and policies regarding positive test findings. 11 tables