In the spring of 1972 almost 18,000 seniors, from over 1,100 public and nonpublic high schools, participated in the first phase of a longitudinal study intended to supply the educational community with facts on the flow of young adults through the postsecondary educational-occupational system. Followup data will be requested from these young adults at intervals over a projected total period of 6-8 years. These data will facilitate the identification of major branching or decision points that affect educational and life patterns in the immediate postsecondary period. Additionally, these data are intended to provide valuable information for planners, policymakers, and educational researchers as a basis for improving the educational system by making it more responsive to students and their needs. The report first describes the planning and development of the study and then presents a brief description of the characteristics, plans, and attitudes of the students as they were about to leave high school. (Author/MLF)