All neonates with necrotizing enterocoltis cared for at Grady Memorial Hospital from July, 1977, through February, 1979, were compared with controls matched for birth weight and time of admission to the nursery, to examine risk factors which have been implicated in the etiology of the disease. Data on maternal history, birth history, and hospital course were uniformly collected and contrasted for 35 cases and 98 controls. Low birth weight was associated with an increased incidence of NEC and an increased case fatality rate. All babies 36 weeks or more at birth were diagnosed by seven days. More immature infants developed the disease later in their hospital course. In addition, preterm babies who developed NEC after 2 weeks of age appear to be smaller and sicker. Factors previously thought to predispose an infant to the development of the disease, such as prolonged rupture of membranes, infectious complications of pregnancy, low Apgar scores, patent ductus arteriosus, and use of umbilical catheters, were found with equal frequency in cases and controls and may simply represent the descriptive characteristics of a population of sick premature infants. Feeding history and antibiotic use were examined in depth and were not correlated with the development of NEC.