The current National Longitudinal Mortality Study began in 1983 with agreements with the Census Bureau which prepared baseline files from surveys representative of the United States and with the National Center for Health Statistics which prepared the National Death Index identifying deaths in the baseline populations. The baseline population of over one million persons has been matched to the NDI on several occasions, resulting in approximately 100,000 deaths occurring in 1979 to 1989. Using available data, an analysis was conducted relating socio-economic characteristics to subsequent mortality.