This study represents an analysis of the principal clinical factors and pathological lesions of 150 cases of necrotic enteritis encountered during 1968 and 1969 in Quebec. Following multiple investigations no common factor was observed which might have explained the pathogenesis of the condition which was observed during every month of the year, especially from May to November. Birds two to four weeks of age were the most susceptible. The main lesion was a fibrino-necrotic enteritis always localized in the small intestine, either in its entire length or just a segment and characterized by the disappearance of the surface epithelium and necrosis of the villi. The lumen was filled with desquamated epithelial cells and bacteria. Foci of coagulation necrosis were observed in the liver and foci of nephrosis in the kidneys. A Gram+ bacillus, strictly anaerobic, was always isolated from the viscera.