A modified case-control study was conducted for selected birth defects that occurred among residents who lived in areas that surrounded two vinyl chloride polymerization facilities in New Jersey. Odds ratios for central nervous system defects (ICD 9, 740-742) decreased as the distance the mothers' residences were located from the facilities increased. Higher odds ratios for central nervous system birth defects were found in the areas around the plant that had higher vinyl chloride emissions. None of the odds ratios, however, were statistically significant. The differences in concentrations of emissions from the different plants may contribute to the discrepancies reported in previous studies wherein the risk of environmental exposure to vinyl chloride was assessed.