One-hundred and fifteen infants aged 1 to 31 days from two intensive-care units were grouped into 6 classes according to clinical criteria (enterocolitis with or without anatomopathological examination and pneumatosis intestinalis, "haemorrhagic colitis", acute diarrhoea or absence of intestinal disorders). The total number of viable bacteria, the number of Clostridium and, in some cases, the presence of rota- and/or coronavirus were determined in their stools. The incidence of Clostridium in the stools of infants with enterocolitis (with or without pneumatosis intestinalis) or haemorrhagic colitis was not significantly different from that of infants without intestinal disorders, whereas stools of infants with acute diarrhoea less often contained Clostridium than those of other infants. C. butyricum, C. difficile, C. perfringens, C. tertium, and C. sordellii were identified. Correspondence analysis comparing the variable, "clinical profile", with 23 other variables, suggested that the variables of gemellity, a birthweight below 1900 g, a gestational age of less than 35 weeks, respiratory distress, umbilical catheterization and a Clostridium count above 10(7)/g at the onset of clinical signs, i.e. between 8 to 12 days of age, were linked to the clinical profile of necrotizing enterocolitis with pneumatosis intestinalis. Conversely, the absence of gemellity, a high birthweight and gestational age, the absence of respiratory distress or umbilical catheterization, the onset of diarrhoea within 8 days, and the presence of rota- and/or coronavirus in the stools were linked with a clinical profile of acute diarrhoea.