The aim of this study was to identify risk factors associated to mortality in newborn stage III necrotizing enterocolitis (NEC III). Neonatal Intensive Care Unit (NICU) at the Hospital de Pediatría CMN Siglo XXI IMSS; Mexico City. Twenty one clinical records were analyzed. A case-control study was realized from patients admitted in the NICU from January to November 1997. Two cases were excluded. The 19 that remained had 52% mortality. They were ten cases and nine controls. They were no significant differences between both groups in gestational age, birth weight, breast or formula feeding, neither X-rays nor whíte blood cells and platelet counts showed differences, except in band-count increase. Anterior abdominal wall celullitis and gut perforation, both had significative differences (p = 0.01); also shock and acute renal failure had an odds ratio of 11.2 and 72, respectively. The NEC mortality in this study is similar to previous communications; nevertheless, the gestational age of these patients is greater than the literature reports. The most significant risk factors found in this paper in relationship to mortality were shock and acute renal failure; both had a high odds ratio.