The National Longitudinal Study (NLS) of the High School Class of 1972 is a large-scale long-term survey effort supported by the National Center for Education Statistics (NCES), Office of the Assistant Secretary for Educational Research and Improvement in the U.S. Department of Education. NLS is designed to provide statistics on a national sample of students as they move out of the American high school system into the critical years of early adulthood. Data have been gathered and colligated from several sources, coded and edited for analysis purposes, and stored on magnetic computer tapes for future access. The current tapes contain base-year (1972) survey data, collected by the Educational Testing Service, integrated with first follow-up (1973), second follow-up (1974), third follow-up (1976), and fourth follow-up (1979) survey data, collected by the Research Triangle Institute. The Users Manual provides a detailed description of the merged NLS data file now available for use by the general research community. These data provide an extensive and potentially rich resource for a variety of research purposes. The purpose of this manual is to document the contents of the available tapes, and thereby enable the interested investigator to exploit effectively the research potential or' the data. The following are appended: (1) Instrumentation: Student's School Record Information Form, Base-Year Student Questionnaire, First Follow-Up Questionnaire (Form B), Second Follow-Up Questionnaire, Activity State Questionnaire, Third Follow-Up Questionnaire, Fourth Follow-Up Questionnaire, and Supplemental Questionnaire; (2) Critical Items and Supporting Items in the First, Second, and Third Follow-Up Questionnaires, and Critical Items in the Fourth Follow-Up Questionnaire; and (3) Miscellaneous Codes, Created Response Categories, and Questions with Resolvable Multiple Responses. [This report was prepared by the Center for Educational Research and Evaluation, Research Triangle Institute.]