Medication-assisted treatment (MAT) is underutilized in the treatment of drug-dependent, criminal justice populations. This study surveyed criminal justice agencies affiliated with the Criminal Justice Drug Abuse Treatment Studies (CJ-DATS) to assess use of MAT and factors influencing use of MAT. A convenience sample (N = 50) of criminal justice agency respondents (e.g., jails, prisons, parole/probation, and drug courts) completed a survey on MAT practices and attitudes. Pregnant women and individuals experiencing withdrawal were most likely to receive MAT for opiate dependence in jail or prison, whereas those reentering the community from jail or prison were the least likely to receive MAT. Factors influencing use of MAT included criminal justice preferences for drug-free treatment, limited knowledge of the benefits of MAT, security concerns, regulations prohibiting use of MAT for certain agencies, and lack of qualified medical staff. Differences across agency type in the factors influencing use and perceptions of MAT were also examined. MAT use is largely limited to detoxification and maintenance of pregnant women in criminal justice settings. Use of MAT during the community reentry period is minimal. Addressing inadequate knowledge and negative attitudes about MAT may increase its adoption, but better linkages to community pharmacotherapy during the reentry period might overcome other issues, including security, liability, staffing, and regulatory concerns. The CJ-DATS collaborative MAT implementation study to address inadequate knowledge, attitudes, and linkage will be described.