A major purpose of the National Longitudinal Study of the High School Class of 1972 (NLS) was to provide a data base for studies concerned with the relationship between high school experience and experience in the years immediately following graduation. This methodological report is designed to facilitate use of the data base. The sample was designed to be as representative as possible of all twelfth graders in the United States in 1972 and included over 18,000 participants from 1,069 schools. The first followup questionnaire asked about educational, employment, and/or military status in October 1972 and 1973. Repeated efforts resulted in a 61% followup response. Two data files were developed: a master file and a release file. Because the NLS sample was stratified, multistage, and clustered, a system of weights was developed to provide unbiased sample estimates; sampling error estimates were developed. Various composite scores were developed for academic ability, socioeconomic status, and psychological attributes. Two methodological studies were concerned with the problem of nonparticipating schools. The final chapter describes some of the results of studies based on the NLS data. The appendices contain an annotated list of 25 followup studies and examples of questionnaires used in the followup. (CTM)