Data from the 1988 National Maternal and Infant Health Survey files were linked with data from the 1990 Environmental Protection Agency National Priorities List of hazardous waste sites to determine whether any relationship existed between living in proximity to hazardous waste sites and low birthweight. The odds ratio for low birthweight versus normal birthweight was 1.03 (95% confidence interval [95% CI] = 0.98-1.16), and remained at 0.99 (95% CI = 0.86-1.16) when adjusted for maternal age, parity, infant sex, prenatal care, and behavioral and socioeconomic factors. Very low birthweight, infant and fetal death, prematurity, and congenital malformation were not found to be associated with living in the vicinity of a hazardous waste site during pregnancy. Merging a large population database with environmental data proved to be an innovative but not very efficient method of assessing the risks of low birthweight related to the environment.