The recent alarming increase in the incidence of neonatal necrotizing enterocolitis has prompted this study of complications in 22 infants treated over a 24-month period. Clinical features of the disease included abdominal distention, vomiting, upper and lower gastrointestinal tract bleeding, pneumatosis intestinalis and/or perforation. Surgical complications occurring in ten infants required 17 major operative procedures. Perforation, due to intestinal necrosis and gangrene, was treated in eight infants with simple closure, exteriorization, or resection. Only one of three infants survived primary anastomosis. Many infants surviving the acute disease suffered late complications, the most serious of which were stricture of both colon and small bowel, enteric fistula, malabsorption, and sepsis. Overall mortality was 27%. Early diagnosis and aggressive treatment of necrotizing enterocolitis may prevent or decrease the severity of these life-threatening complications.