The purpose of this paper is to provide a detailed description of the Monitoring the Future research design, including sampling design, data collection procedures, measurement content, and questionnaire format. This study assesses the changing lifestyles, values, and preferences of American youth on a continuing basis. Each year since 1975, at least 13,000 seniors have participated in the annual survey, which is conducted in some 120 to 140 high schools nationwide. Since 1991, the study's annual surveys also have included surveys of similar nationally representative samples of eighth- and tenth- grade students. In addition, subsamples of seniors from previously participating classes receive follow-up questionnaires by mail each year. [For the objectives and theoretical foundation for the Monitoring the Future Study, see "The Objectives and Theoretical Foundation of the Monitoring the Future Study. Monitoring the Future Occasional Paper Series. Paper 84," ED578426.]