Objective/Method: The use of brief, reliable, valid, and practical measures of substance use is critical for conducting individual assessments and program evaluation for integrated mental health-substance abuse services for persons with serious mental illness. This investigation examines the internal consistency reliability, concurrent validity, and receiver operating characteristics of the Alcohol Use Disorders Identification Test (AUDIT) with 149 mentally ill adults in community programs. Results/Conclusions: Results suggest that the AUDIT is a reliable screening tool and shows good concurrent validity with other measures of alcohol abuse and psychosocial difficulties. In addition, receiver operating characteristics suggest that, for this population, a lower cutoff score ([greater than or equal] 3) leads to more accurate detection of an alcohol use disorder (based on the Alcohol Use Scale) than the traditional cutoff ([greater than or equal] 8). This article discusses implications for using screens routinely as part of assessment and evaluation with this population. (Contains 1 table.)