Prevalence estimates were obtained to assess drug use, with emphasis on marijuana, hallucinogens, cocaine, heroin, nonmedical use of prescription drugs, and psychotherapeutic drugs (stimulants, sedatives, tranquilizers, and analgesics). Actual sampling of the household population was carried out using a national area probability sample. Sample locations, households, and specific youths and adults to be interviewed were designated by the sampling plan and through instructions to the interviewer. Interviewers visited selected households in order to list residents for purposes of random selection. Response rates for youth, adults between 18 and 34 years of age, and adults 35 years of age and older were 84 percent, 81 percent, and 77 percent, respectively. Data indicated a reversal in upward drug use trends charted by earlier national surveys conducted in the 1970's. Between 1979 and 1982, marijuana use by the youth population leveled off and there was a significant decline in the percentage of persons who currently used marijuana, alcohol, and various other drugs. Persons who tried illicit drugs such as hallucinogens, cocaine, and heroin almost always represented a subset of those who tried marijuana. Levels of drug use opportunity remained high in 1982, with marijuana opportunity a commonplace experience. Detailed data are provided on the use of marijuana, hallucinogens, cocaine, heroin, psychotherapeutics, alcohol, and cigarettes. The survey questionnaire is included. 80 tables