Data were collected from high school seniors in approximately 125 to 140 public and private schools during the spring of each year, beginning with the class of 1975. A three-stage sampling procedure was used to secure a nationwide sample. From 77 to 83 percent of all sampled students completed the questionnaires. The report not only covers current drug use, but provides data on grade of first use; trends in use at earlier grade levels; intensity of drug use; seniors' attitudes and beliefs regarding harmfulness of drugs; and trends in disapproval of drug use among seniors, parents, and peers. Statistics distinguish 11 separate classes of drugs, marijuana, inhalants, hallucinogens, cocaine, heroin, natural and synthetic opiates other than heroin, stimulants, sedatives, tranquilizers, alcohol, and cigarettes. Special sections deal with the use of nonprescription stimulants like diet or stay-awake pills and the results of a set of questions on the use of marijuana at a daily or near-daily level. Footnotes, graphs, and 21 tables.