The effect of race on the relationship between fetal death and altered fetal growth. This population study examines racial differences in the relationship between birth weight and fetal death. An earlier report showed that a birth weight that results in a fourfold increased risk of stillbirth is not a constant birth weight percentile (2nd percentile at 25 weeks, 17th percentile at 42 weeks). This analysis was applied to 782,430 white and black births in Illinois from 1980 to 1984. Mean and 10th percentile growth for white and black infants is identical before 34 weeks' gestation and growth diverges by 250 gm at term, with white infants being larger. Race-specific birth weights resulting in quadrupling of the stillbirth rate were determined with an exponential regression analysis of the relationship between birth weight and fetal death rate for each gestational age. The data indicate (1) that the birth weights resulting in quadrupling the stillbirth rate are substantially above the Denver 10th percentile and the previously unpublished race-specific Illinois 10th percentiles and (2) that at term white infants demonstrate this constant risk at the 12th percentile, whereas black infants exhibit the risk at the 18th percentile. From these data we conclude that black fetuses are more sensitive than white fetuses to factors that adversely affect growth and that continued use of "race-neutral" data for clinical management in racially heterogenous populations will not accurately predict the risk of stillbirth. 