Confirmatory factor analysis was used to test the scale structure of the Addiction Severity Index (ASI) in a sample of 1,802 substance abusers (43% alcohol dependent) with a concurrent psychiatric disorder (46% with mood disorders). The fit of the original composite score model based on the work of P. L. McGahan, J. A. Griffith, R. Parente, and A. T. McLellan (1990) was compared with the evaluation indices (EIs) developed by A. I. Alterman et al. (1998). The 5-dimensional model based on the EIs was an overall better fit to the data. Internal consistency (Cronbach's alpha) for the EIs ranged from.66 (family domain) to.75 (legal domain). The 5 EIs were moderately correlated (rs =.42-.72) with the interviewer severity ratings from the ASI. Evaluation studies involving concurrent disordered substance abusers should use the EIs as summary measures of change.