This article reports on a study of Federal defendants who were court ordered to complete a 28-day residential drug treatment program as a condition of pretrial release in 1990-91 in the Eastern District of Pennsylvania. The study was conducted to determine how effective this condition of pretrial release is in meeting with the objectives of the Bail Reform Act of 1984, i.e., in assuring the defendant's appearance in court and the safety of any other person and the community. The study, conducted by the U.S. Pretrial Services Office for the Eastern District of Pennsylvania, centers on defendants sent to the Mirmont Residential Treatment Program located approximately 20 miles from downtown Philadelphia. The first objective of the research was to determine the number of defendants who violated and the types of violations committed. The second objective was to gain insight into the characteristics of defendants who violate. The third objective was to obtain information about the referral and supervision process to enable pretrial services to develop new policies to provide more effective supervision of defendants sent to residential drug treatment programs. The study revealed, inter alia, that females violated at a higher rate than males overall. Women also failed to appear at almost twice the rate of men. Women, however, had a significantly lower rate of testing positive for illegal drugs. Overall, violations were not affected by the drug the defendant used. Defendants without prior arrests and defendants without prior convictions violated at higher rates than those with prior arrests and convictions. Based on these and other preliminary findings, new policies have been introduced at Mirmont which are discussed in the article. Tables, notes, references