A prospective investigation was conducted to determine if infants with necrotizing enterocolitis had evidence of carbohydrate intolerance prior to the onset of clinical symptoms of advanced disease. Stool specimens were examined for fecal reducing substances with Clintest tablets from well, full-term infants and sick premature infants. Only two of 45 (4.4%) formula-fed, full-term infants demonstrated higher than 2+ fecal reducing substances. Ten of 14 (71%) formula-fed premature infants who developed necrotizing enterocolitis had higher than 2+ reducing substances detected in their stools. Daily measurement of fecal reducing substances can be a useful adjunct in the management of sick premature infants.