An outbreak of necrotizing enterocolitis (NEC) occurred in 6 neonates within a 2-month period. Blood cultures from 3 of these neonates grew the same strain of what appears to be a novel clostridial species for which the name "Clostridium neonatale" has been proposed. A point-prevalence survey that used rectal swabs was performed in our intensive-care and intermediate-care nurseries, and it indicated that 20.8% of neonates carried this same "C. neonatale" strain despite having no evidence of NEC. In conclusion, we describe an outbreak of NEC associated with the novel species, and we suggest that, in larger neonates, carriage of this type of Clostridium species may be a necessary step in the multistage pathogenesis of NEC.