In addition to assessing drug use prevalence and trends, the Substance Abuse and Mental Health Services Administration of the U.S. Department of Health and Human Services uses NHSDA data to investigate many special topics that are important for understanding the nature of drug abuse. Despite the value of the NHSDA for national statistics, however, the survey by itself is not an adequate source of information about drug abuse at State and Metropolitan Statistical Area (MSA) levels. For that reason, algorithms have been developed in mathematical models that relate available local data to drug abuse measured in the NHSDA. Methods and procedures used in the NHSDA are described, and detailed mathematical formulations are provided. Appendixes contain further information on the classification of drug and alcohol dependence, MSA definitions, technical information on the computer software used in mathematical calculations, information on geographic predictors of drug and alcohol abuse, tables of actual estimates for States and MSA's, and tables of confidence intervals. Reference, tables, and exhibits