The Addiction Severity Index (ASI) is 12 years old and has been revised to include a new section on family history of alcohol, drug, and psychiatric problems. New items were added in existing sections to assess route of drug administration; additional illegal activities; emotional, physical, and sexual abuse; quality of the recovery environment; and history of close personal relationships. No changes were made in the composite scoring to maintain comparability with previous editions. This article discusses the clinical and research uses of the ASI over the past 12 years, emphasizing some special circumstances that affect its administration. The article then describes the rationale for and description of the changes made in the ASI. The final section provides "normative data" on the composite scores and severity ratings for samples of opiate, alcohol, and cocaine abusers as well as drug abusing inmates, pregnant women, homeless men, and psychiatrically ill substance abusers.