A total of 498 children, aged 0-14 years, admitted at the B.C. Roy Memorial Hospital for Children, Calcutta, were investigated for the occurrence of Clostridium difficile and its cytotoxin. Of the children in the investigation, 369 suffered from acute diarrhea. Only 8.4% of these children had C. difficile in fecal samples and in vitro cytotoxin was demonstrated in 7%. In 27 (7.3%) of the patients with acute diarrhea C. difficile was isolated as the only pathogen. In contrast, among 129 control children not suffering from acute diarrhea, only 4 (3.1%) harboured C. difficile. Isolation of C. difficile was significantly higher in children under one year of age. None of these patients had any history of prior antibiotic therapy.