The incidence of necrotizing enterocolitis in the newborn infant has increased within the same time period that increasing emphasis has been placed on oral alimentation of very small infants. A prospective investigation was conducted to determine the nutritional efficacy as well as the incidence of necrotizing enterocolitis of a standard cow milk formula compared with an elemental formula. Sixteen infants who weighed less than 1,200 gm were randomized and fed one of the two formulas. The clinical status of the two groups was similar. Seven of eight (87.5%) infants fed the elemental formula and two of eitht (25%) fed the standard cow milk formula developed necrotizing enterocolitis (p less than 0.02). The hypertonicity of the elemental diet may have contributed to the increased incidence of necrotizing enterocolitis in infants fed this formula.