The two reports contained in this document are products of the 1988 National Household Survey on Drug Abuse, the ninth in a series of national surveys designed to measure the prevalence of drug use among the American household population aged 12 and over. The Main Findings report provides details of the National Household Survey methodology as well as information on prevalence, trends, and correlates of drug use. The Population Estimates report presents estimates of drug use prevalence for the civilian and noninstitutionalized population of the United States, presenting estimates separately first for the total population and then for Whites, Hispanics, and Blacks. For each drug there are eight tables which are arranged to facilitate group comparisons. The data for the total population are presented by sex for each of the four age groups. Data in the remaining seven tables for each racial or regional category are presented first by age, then by sex, and finally for the total population in that racial or regional category. A section on prevalence estimates for specific drugs presents data for the illicit use of any drug. This is followed by data for the prevalence of the individual licit and illicit drugs. The frequency and regularity of drug use among past year users are documented. Data is also provided on the frequency of use in the past year for marijuana, cocaine, and alcohol. (LLL)