The results of the twenty-first national survey of drug use and related attitudes among U.S. high school students are reported. This volume contains the results from the secondary school samples taken from eighth, tenth, and twelfth graders. All the data come from an ongoing national research and reporting program. Distinctions are made among important demographic subgroups in these populations. Data on grade level of first use, trends in use at lower grade levels, and intensity of drug use also are reported. Key attitudes and beliefs about drug use and perceptions of certain relevant aspects of the social environment are included as potential explanatory factors. Initially, 11 separate classes of drugs were distinguished for this series of reports. For drugs other than alcohol–cigarettes, smokeless tobacco, inhalants, and nonprescription stimulants–most of the information deals with illicit use of controlled substances. The emphasis here is on drug use at the higher frequency levels. Appendices provide data for calculating statistical accuracy. Statistics are presented in 40 tables. (RJM)