This report provides evidence concerning the projected demand for substance abuse treatment services for older Americans over the next 20 to 30 years and suggests approaches for refining these projections. A work group of Federal agency representatives and university researchers was established by the Substance Abuse and Mental Health Services Administration, Office of Applied Studies, to examine and assess the ability of available data to provide sufficient information to guide planning to address the possible doubling of the number of those older adults requiring substance abuse treatment services. The work group identified and reviewed available information, gaps in data, assumptions concerning data collection and analysis, important variables, and estimation methods and models. This report includes original analyses of a wide variety of data sources undertaken by an invited panel of experts. The chapters in this report review the issues in anticipation of the substance abuse treatment needs of the future elderly. The report highlights uses of available data and provides examples of analyses and methodological issues required to refine forecasts of the demand for substance abuse treatment services emerging over the next several decades. The final chapter discusses the implications and suggests approaches to extending our knowledge in the area. (Contains 209 references and 29 tables.) (GCP)