A systematic and comprehensive review of all 320 perinatal deaths occurring in Nassau County [New York, USA] in 1973 revealed that 1/4 of these deaths might have been prevented in modalities of care that were known and available at that time had been utilized appropriately. Preventability, the presence or absence of avoidable factors which might have materially lessened the risk of death, was determined for each perinatal death. Preventable deaths were disproportionately higher among postmature (P. < .01) and large-for-gestational-age (P < .05) perinatal deaths, neonatal deaths, neonatal deaths after the 1st day of life (P < .05), intrapartum fetal deaths (P < .01), and perinatal deaths secondary to anoxia and idiopathic respiratory distress syndrome (P < .01). Rigorous application of currently available medical knowledge, the establishment of local perinatal mortality review communities, and vigorous outreach to practitioners are urgently needed to bridge the time gap between the development of new modalities of care and their application.