Monitoring drug-abuse-treatment delivery and progress requires the use of validated instruments to measure client motivation, psychosocial and cognitive functioning, and other treatment-process dynamics. As part of the National Institute on Drug Abuse Criminal Justice Drug Abuse Treatment Studies project for examining client-performance indicators for treatment of correctional populations, this study examined psychometric properties of the Criminal Justice Client Evaluation of Self and Treatment (CJ CEST). The sample included 3,266 offenders from 26 corrections-based treatment programs located in six states. Overall, the client assessment demonstrated good reliabilities evaluated at the individual and program levels and in test-retest administrations. In addition, evidence for construct validity was favorable. It is concluded that the CJ CEST is a brief yet comprehensive instrument that effectively and efficiently measures client needs and functioning at intake and also is appropriate for use during treatment to monitor progress over time in corrections-based drug-treatment programs.