As part of a six-site effort sponsored by the Bureau of Justice Assistance, demonstration projects at the two sites sought to implement drug testing programs at the prebail and pretrial releases stages of the criminal process to deter pretrial misconduct (failure to appear in court and rearrest for crimes during pretrial release). Projects hypothesized that prebail drug testing would contribute powerful predictive data for use by pretrial release decisionmakers in assessing risks posed by defendants and that pretrial drug monitoring during pretrial release would deter defendants from crime and flight better than release without drug monitoring. Experimental results did not support either hypothesis, but the authors determined that the findings could not be meaningfully interpreted in isolation from knowledge of the implementation context at the two sites. In fact, both demonstration projects faced challenging obstacles in implementing the projects as planned. The need to take into account difficulties posed by the challenges of implementing new programs, however, did not undermine the strength of the reported findings. Rather, implementation difficulties in themselves were seen as important findings concerning the feasibility of pretrial drug testing programs. 36 references, 38 notes, and 10 tables