I. INTRODUCTION

The Population Estimates report is published by the Office of Applied Studies (OAS) within the Substance Abuse and Mental Health Services Administration (SAMHSA). The report provides the drug abuse prevention, treatment, and research communities, and other interested parties, with timely data on current substance use prevalence measures. OAS issues a companion volume, the Main Findings report, at a later date to present an expanded analysis of the data, including information on drug and alcohol use trends; demographic correlates of use of illicit drugs, alcohol, and tobacco; patterns and problems of drug use; and perceived harmfulness of drug use. OAS produces and distributes another NHSDA report containing prevalence estimates when the survey results are first released each year. Special analytic reports also are periodically produced on topics of current interest (e.g., drug use among employed people, drug use and family structure).

Estimates presented in Sections III and IV of this report are based on a questionnaire and estimation methodology introduced in 1994 and continued through 1998.1 Due to the effect this new methodology may have on the magnitude of estimates, comparisons with NHSDA data prior to 1994 should be made with caution.2

1 See page 9 of the following: Office of Applied Studies, Substance Abuse and Mental Health Services
Administration. (1995). National Household Survey on Drug Abuse: Population estimates 1994
(DHHS Publication No. SMA 95-3063). Rockville, MD: Author.
2 For additional detailed information on the 1994 questionnaire modification and its implications, see the
following: Office of Applied Studies, Substance Abuse and Mental Health Services Administration.
(1996). The development and implementation of a new data collection instrument for the 1994 National
Household Survey on Drug Abuse (DHHS Publication No. SMA 96-3084). Rockville, MD: Author.