The National Longitudinal Surveys (NLS), sponsored by the Bureau of Labor Statistics, U.S. Department of Labor, are a set of surveys each of which has gathered information at multiple points in time on the labor market experiences of five groups of men and women since the mid-1960s. Each group of at least 5,000 persons was selected to be representative of all U.S. citizens born during a given time period such that conclusions about the sample group would be generalizable to the experiences of the larger population. This handbook introduces the reader to the NLS project and the various data sets that comprise the NLS. It is designed to help readers make an informed decision on whether the NLS is an appropriate data source for their research needs and to provide additional resources for those who want more information. This handbook is organized in eight section. The first section presents a general introduction to the NLS and to this handbook. Sections 2, 3, and 4 overview the NLS samples: the NLSY (Youth), the NLSY mothers and children, and the four original cohorts. Each section provides information on the samples, the interviews, and the major data elements available within each data set. Section 5 presents a bibliographic listing of recently published research based on data from the NLSY, the NLSY children, and the four original cohorts. Sections 6 and 7 describe the NLS compact disks, magnetic tapes, and documentation items available to the research community. Section 8 directs the reader to other publications, technical manuals, and reports that provide more information on the NLS. The manual includes 20 tables and 203 references. (KC)