The subject is introduced by a brief historical resumé and account of campylobacter enterocolitis in man. Published figures on the prevalence of campylobacters in normal dogs and cats show a wide range. It is highest (49% dogs, 45% cats) in immature animals, particularly strays or those living in kennels, and lowest (less than 1.6% dogs and cats) in adult animals living in households. Several studies have shown no significant difference between the prevalence in normal animals and those suffering from diarrhoea, but two surveys did show such a difference. It seems that while most animals are unaffected by infection with campylobacters, a few suffer an illness like that seen in man. Longitudinal studies to determine incidence--as opposed to prevalence--of infection are required. A small proportion of human infections are acquired from dogs. These are usually puppies that are themselves suffering from diarrhoea. Only four infections associated with cats (all kittens with diarrhoea) have been reported. Contact is invariably close and the victims are often small children. The application of simple hygienic measures should prevent such infections.