There is growing evidence that equine dysautonomia is a toxicoinfection with Clostridium botulinum type C. The possibility that feline dysautonomia has the same aetiology was investigated by attempting to detect botulinum type C neurotoxin in the food, faeces and the contents of the ileum of affected cats, and by serology. The toxin was detected directly in four of eight affected cats and after enrichment in seven of them, and in their dried food. No toxin was detected in healthy control cats or in their tinned food. Recent exposure to the organism was assessed by the detection of immunoglobulin A (IgA) in the faeces of healthy control cats and affected cats. The levels of IgA antibodies to the toxin and to surface antigens of C. botulinum type C in the faeces of the affected cats 14 weeks after the outbreak were significantly higher than in the faeces of the control cats.