Serial determinations of the absolute granulocyte and platelet counts were performed in 40 infants with severe neonatal necrotizing enterocolitis. Fourteen of the 38 infants had absolute granulocyte counts less than 1,500 nm3, the mean absolute granulocyte count was significantly lower in the group of infants who died during the acute episode of NEC as compared to that of the infants who survived. Thrity-five of 40 infants had nadir platelet counts less than 150,000/nm3, clinical bleeding occurred in 12 of the thrombocytopenic infants. Fourteen thrombocytopenic infants were evaluated for disseminated intravascular coagulation by additional coagulation studies; six were noted to have laboratory evidence of DIC. We conclude that (1) a low absolute granulocyte count in severe NEC is associated with a poor prognosis and (2) thrombocytopenia is a significant problem in severe NEC and may occur with or without evidence of fulminant intravascular coagulation.