The National Longitudinal Transition Study of Special Education Students (NLTS) provides information to practitioners, policymakers, researchers, and others in the special education community regarding the transition of youth with disabilities from secondary school to early adulthood. The sample for the study, which began in 1987, involves more than 8,000 youth from the national population of special education students in the 1985-86 school year who were at least 13 years old. Data from these students will be collected again in 1990. The primary research questions involve identifying factors that contribute to the effective transition from secondary school to employment, further education, and independent living. This report documents the data collection and data processing procedures used in developing the primary database for the NLTS. Four data components were used to obtain the data specified by the conceptual framework: (1) parent/guardian interviews; (2) data from school records; (3) a survey of secondary special education programs; and (4) survey of non-respondents. The combined database includes data from at least one source for 8,678 youth, 84% of the initial sample. Complete data from the parent interview, school records, and school survey are provided for 4,064 youth. Data collection instruments and accompanying materials are presented in three extensive appendices. (SLD)