To evaluate the relationship between management of delivery and neonatal outcome in singleton [human] neonates with birth weights between 501 and 1000 g, a retrospective analysis was performed. In the 54-mo. period ending June 30, 1981, a total of 109 singleton neonates were born at Vanderbilt University Hospital, Nashville, Tennessee [USA] with birth weights between 501 and 1000 g, 31 weighing 501 through 750 g and 78 weighing 751 through 1000 g. The overall neonatal survival rate was 60%, 39% in the group weighing 501 through 750 g and 69% in the group weighing 751 through 1000 g. In terms of morbidity and mortality, there was no difference between neonates delivered by cesarean section compared with those delivered vaginally. The only significant factor relating to neonatal mortality was the occurrence of labor. In the 17 newborns delivered without occurrence of labor, the frequency of neonatal death was significantly decreased, although this difference may be caused by differing risk factors in the infants delivered without occurrence of labor. When labor was present and the fetus had a cephalic prsentation, cesarean section was not superior to vaginal delivery in terms of neonatal morbidity or mortality for neonates of 1000 g or less.