Respondents were interviewed in their homes by trained interviewers using self-administered answer sheets and other methodologies intended to maximize the validity of responses to sensitive questions. Respondents were drawn randomly within age categories from a national probability sample of households in the coterminous United States. Data were collected from June through December 1985, resulting in 8,038 interviews and an overall response rate of 83 percent. Age and race/ethnicity were the two primary correlates of drug use on which the 1985 sample was stratified. Younger age groups, blacks, and Hispanics were oversampled to obtain more stable estimates of drug use for them. Population estimates are presented for the total population and for whites, Hispanics, and blacks. Data are also presented for the Northeast, North Central, South, and West regions of the United States. Data in each table are presented by sex for each of four age groups (12-17, 18-25, 26-34, and 35+ years). Tables are organized into three sections: prevalence estimates for specific drugs; prevalence estimates of illicit drug users; and frequency of drug use among past year users. 128 tables.