One hundred one infants requiring operative treatment for necrotizing enterocolitis were evaluated for prenatal, perinatal, therapeutic, clinical, laboratory, radiographic, and operative factors as they relate to mortality. Infants less than 28 weeks gestation and those with birth weight less than 1500 gm had an increased mortality rate. The use of umbilical arterial catheters, high-density premature formulas, and aminophylline (for apnea) had an adverse effect on survival. Persistent acidosis, oliguria, and abdominal wall erythema resulted in a significantly worse outcome. The presence of portal vein air on abdominal radiograph was associated with a 71% mortality rate. The survival rate in infants with localized involvement was 70%. Thirty-eight percent of patients had extensive bowel involvement and a greater than 95% mortality rate. Avoidance of enteral feedings, cautious use of umbilical artery catheters, and judicious application of pharmacologic agents in infants at risk for necrotizing enterocolitis is of importance with regard to prevention. While medical management is feasible in some cases, persistent acidosis, oliguria, abdominal wall erythema, and portal vein air are associated with advanced disease. Infants with these risk factors should be candidates for prompt operative intervention.