A case of chronic intermittent diarrhoea in a dog is reported. Large numbers of Clostridium perfringens type A were recovered from the faeces. A toxin neutralised by C perfringens type A antitoxin was demonstrated in the same samples. No clear predisposing factors contributing to the condition could be determined. The dog recovered following a 10 day course of metronidazole at 20 mg/kg/day per os and a change to a bland diet.