Three hundred two infants with necrotizing enterocolitis (NEC) were treated from 1972 to 1990. One hundred eighteen were treated medically while 184 infants required operation. Comparisons were made between two treatment periods, 1972 to 1982 (n = 176) and 1983 to 1990 (n = 126). Infants in the more recent era were of lower birth weight (1505 +/- 853 g versus 1645 +/- 836 g), earlier gestational age (30.4 +/- 4.7 weeks versus 32.4.5 weeks; [p less than 0.01]), had symptom onset at an older age (15.7 +/- 13.9 days versus 10.0 +/- 10.8 days; [p less than 0.001]), and a lower incidence of hyaline membrane disease (p less than 0.001). Fewer patients in the 1983 to 1990 group had acidosis (p less than 0.001) and severe oliguria (p less than 0.001). Operation was performed sooner after diagnosis in the second group (2.6 versus 3.8 days; [p less than 0.001]). Survival was unaffected by sex, maternal complications, or whether infants were inborn or transferred from other facilities. Improved survival (1983 to 1990) was observed in those infants between 24 to 27 weeks gestation (p less than 0.002) and those weighing less than 1000 g (p less than 0.001). Since 1983 portal vein air (PVA) on abdominal radiographs was used as an indicator for operation. Survival in infants with PVA has improved from 29% to 64% (p less than 0.02). Despite patients being more immature and weighing less, the overall survival rate improved from 58% (1972 to 1982) to 82% (1983 to 1990) (p less than 0.001). Operative survival rate improved from 51% to 75% (p less than 0.002). Long-term survival was 75% overall and 65% for surgical infants in the 1983 to 1990 group (p less than 0.05).