The Addiction Severity Index (ASI) has become one of the most widely used instruments in the addictions field. As a result of its wide popularity, there are multiple versions of the instrument in use, and a wide range of computer systems used to collect and/or store ASI data. Thus, it has been difficult for different users and systems to share ASI data. This difficulty significantly reduces the value of the information for treatment providers, policy makers, and researchers. This article provides operational definitions and specifications for a "Standard ASI Database." Descriptions for standard variable names, data types, field lengths, value labels, range checks, and programming notes for all items in the fifth edition of the ASI are available electronically from the senior. Examples from the full protocol and the rationale for producing the Standard ASI Database elements are illustrated here. It is hoped that the format suggested will become the "industry standard" for ASI data storage among all users of the ASI and that, regardless of the software used or the method of data collection, there will be a single, standard format for all ASI databases. The potential applications from such a database would benefit treatment providers/clinicians and researchers as well as payers and policy makers. (C) 2001 Elsevier Science Inc. All rights reserved.