To determine who is dead or alive, many researchers, policy makers, and corporations have relied on the National Death Index (NDI). This study investigates the impact of using NDI information to establish mortality status upon longevity analyses. A community sample of 694 individuals, enrolled in the Ohio Longitudinal Study of Aging and Retirement in 1975, participated. The authors compared the survival of two groups of these participants: those for whom death information came from clear matches with NDI and those for whom death information was based on both NDI information and supplementary information, such as community informants. Those in the expanded group tended to have significantly shorter survival than those in the strict group. Findings suggest that using limited NDI information alone may falsely increase longevity. Use of NDI offers numerous benefits, but incomplete or inaccurate classification of mortality status may affect study results.