Necrotizing enterocolitis continues to be a perplexing problem in the newborn and, in particular, the premature. Its pathogenesis is controversial, although there are well established clinical risk factors. Three patients had necrotizing enterocolitis while under close clinical observation and monitoring, despite the fact that these patients were not at high risk for necrotizing enterocolitis. All three had necrotizing enterocolitis after hypothermia and total circulatory arrest--a complication which until now has not been reported. Because of the close monitoring, these patients provide a unique clinical setting which eliminates most of the etiologic factors that have been implicated in the pathogenesis of necrotizing enterocolitis. The onset of necrotizing enterocolitis shortly after total circulatory arrest and the selective ischemic organ damage observed suggest local perfusion inadequacy. The authors postulate that splanchnic vasoconstriction as a result of marked sympathetic stimulation contributes to this local ischemia and subsequent necrotizing enterocolitis.