Six weeks after premature birth, a female infant who was being treated in the neonatal intensive care unit was found to have severe abdominal distention. She had been born at 23 weeks of gestation by emergency cesarean section because of premature rupture of membranes; her weight was 520 g at birth. She had been growing well with a combination of enteral feeding and parenteral nutrition. At the time that the abdominal distention developed, plain radiography showed dilated loops of small bowel, and abdominal ultrasonography indicated possible perforation. Exploratory laparotomy was performed, and a diagnosis of necrotizing enterocolitis was made. Necrotizing enterocolitis is characterized by inflammation of the intestinal mucosa and can result in bowel necrosis and perforation; it remains an important cause of complications and death in neonates, especially among preterm infants. The affected bowel segment was resected, and an ileostomy was performed. Four months later, the patient underwent ileostomy reversal and was able to feed fully by mouth at the time of discharge. At the 2-year follow-up, she was growing well.