The National Center for Health Statistics Linked Birth and Infant Death Data Set, 1983 birth cohort, shows that infants weighing less than 750 g, comprising only 0.3% of all births, account for 25% of deaths in the first year of life and for 41% of deaths in the first week. If interventions had prevented the death of these very small babies, the infant mortality rate would have been 8.3 per 1000 live births instead of 10.9, and the Black/White mortality differential would have been reduced by 25%.