Policy makers and practitioners are using treatment outcome data to document the necessity and value of clinical interventions. Existing instruments that measure constructs related to outcomes of substance abuse treatment are often too lengthy, require professional training, and are not used routinely. Administrative data sets may provide an important resource in the assessment of treatment services for alcohol and drug dependence. Data were abstracted from the management information system (MIS) maintained by the Massachusetts Department of Public Health’s Bureau of Substance Abuse Services. Three variables were identified as associated with severity of use: age of first substance use, last regular use, and frequency of last regular use. The hypothesis was that a younger age of onset with a more recent use of the substance and a greater frequency of last regular use would yield a higher measure of the elevated severity for a given case. The Addiction Severity Index (ASI) is a structured interview developed to provide standardized evaluation for patients entering substance abuse treatment. It measures the severity of drug and alcohol use and five related problem areas: family/social, legal, psychiatric, employment, and medical. Results show that age of first alcohol intoxication, last regular alcohol use, and frequency of last regular alcohol use were all strongly correlated with the ASI alcohol indicators and negatively correlated with the ASI drug indicators. Results also indicate that the Severity Index constructed from the administrative database corresponded well with the ASI severity composite scores and ASI interviewers’ severity ratings. The index was also well correlated with reports of drug injection, showing concurrent as well as discriminatory value. One of the benefits of using a severity index derived from administrative data is that it allows comparisons across different sites and modalities without adding to the burden on care givers and clients or requiring any additional resources. 4 tables, 26 references, appendix