This manual contains materials related to the Second Institute for Demographic and Economic Studies, Inc. (IDES) Survey of Experiences and Plans (Winter 1978-79), third in a series of studies of a national sample of young people. The first two surveys are also addressed: survey of high school juniors in spring 1973 by American College Testing Program and first followup by IDES in spring 1976. Information is presented on methodology of the second survey, data file preparation, and technical description of the file, A Longitudinal Survey of Experiences and Plans, with which has been merged the information gathered in the surveys. Appendix A contains the three questionnaires. Appendix B consists of a brief description of the data tape positions corresponding to the first two surveys. The tape layout and frequency distributions of the respondents' answers for the Second IDES Survey are included in appendix C. Appendix D presents the frequency distributions for the more detailed job, industry, and educational field questions separately. Appendixes E, F, and G discuss various aspects of the processing of survey results: (1) verification and correction of routing question responses, (2) dependent questions and legitimate skips, and (3) generating the wage rate variables. The Index of the Second IDES Survey questionnaire in appendix H provides a guide to the scope and coverage of the survey. (YLB)