The bacterium Clostridium chauvoei causes disease in certain animals, most frequently in cattle and sheep. It occurs rarely in pigs, while equines and poultry appear to be resistant to infection. Two cases are presented in which C. chauvoei was isolated from disease of complex aetiology in hens. In Case I, 15-week-old light hybrid chickens were affected with chronic respiratory disease, coccidiosis, ascariasis and inflammation of the skin on the head, with necrosis of the comb. Growth was uneven and mortality reached 24%. Clostridium chauvoei was isolated from two of three combs examined. In Case II a flock of broiler breeders aged 11 weeks developed coccidiosis and, owing to disease or death, 60% were excluded from production. Clostridium chauvoei was isolated from all of 10 livers examined. These results demonstrate that C. chauvoei can infect chickens and that its possible role as a pathogen under certain circumstances should be further investigated.