Treatment providers need tools that are designed to identify risk, treatment needs, and monitor client engagement. These are essential components in substance abuse treatment for offender populations. In this study, the authors evaluated a flexible set of one-page modular assessments known as the Texas Christian University (TCU) Short Forms and compared them with the measures of global domains contained in the Addiction Severity Index (ASI). The sample was based on 540 adult males and females in corrections-based substance abuse treatment services located in Arkansas and Missouri. Results suggest the set of TCU forms and ASI both reliably represent core clinical domains, but TCU Short Forms explained more variance in therapeutic engagement criteria measured during treatment. Similarities and differences of the assessment tools are discussed, along with applications. (Contains 2 tables.)