Clostridium difficile toxin was detected in the feces of 10.5% of normal newborn infants and 55% of neonates in the intensive care unit. None of the normal infants and less than one-third of those in the NICU had any signs of enteric illness. Vaginal delivery and breast-feeding were associated with increased rates of toxin carriage. Although toxin was not detected during antibiotic therapy, it could be found in 85% of infants two weeks or more, and for at least an additional two months, following exposure to antibiotics.