The National Longitudinal surveys (NLS) of Labor Market Behavior have been conducted by the Center for Human Resource Research at Ohio State University and supported by the Department of Labor since l966. In this paper, data from the fifth and newest NLS cohort, a national cohort of 12,686 youth who were aged 14-21 in 1979, are discussed. Approximately 11,400 young men and women from all 50 states and the District of Columbia made up the civilian sample; an additional 1,300 youth in the armed forces were selected for interviewing under funding from the Department of Defense and the Services. The interdisciplinary nature of the Center's research staff, the interests of the agencies who helped fund the survey, and an interest in maintaining comparability with the first four cohorts in terms of human capital and other sociometric variables, labor market experience variables, and environmental variables are reflected in the survey's content. Three additional data sets on school characteristics, student transcripts, and scores on the Armed Services Vocational Aptitude Battery were collected for use with the longitudinal interviews. The 6,500 variables represented in these NLS youth tapes present a challenge to educational researchers using the tapes to develop meaningful longitudinal research problems. (LC)