During the period between October 1985 and August 1986 the Bureau of the Census constructed the first longitudinal data file based on the Survey of Income and Program Participation (SIPP). The data file was created by linking together cross-sectional WAVE-file data and then performing a series of longitudinal edits. Longitudinal edits were implemented to improve consistency for a select group of data items and to correct for a small number of errors related to the cross-sectional processing system. The main objective of this first longitudinal effort was to provide a data base for research and evaluation on SIPP data quality and for exploration of the uses of intra-year income, household composition, and work experience data.