Although race and preterm delivery are known to be associated with sudden infant death syndrome (SIDS), the relationships between age at death from SIDS and these factors have not been well described. To examine these relationships, we used linked infant birth and death records for the cohort of 1,204,375 White and 283,776 Black postneonates who were born from 1979 to 1981 in five states: California, Georgia, Missouri, South Carolina and Tennessee. Deaths attributable to SIDS occurred to 1404 White postneonates and to 696 Black postneonates. Although postneonatal SIDS rate among Black infants was twice that of White infants, the relative risk was smaller among infants with gestations of less than 35 weeks. For White postneonates, the median postneonatal age at death sharply declined for gestations from 28-29 weeks to 36-37 weeks and levelled off for longer gestations. For Black postneonates, the results do not support an association between length of gestation and age at death. The findings suggest that practitioners investigating approaches to avert SIDS need to maintain their interventions to an older age among White preterm infants. Researchers investigating the causes of SIDS need to consider the relationship between length of gestation and age at death from SIDS as well as possible developmental differences between White and Black preterm infants.