Using a selective medium, the epidemiology of Corynebacterium equi in horses was studied. Twelve horse studs in different geographical locations were investigated. In addition, a group of horses was monitored over a period of time to determine whether faecal carriage of C equi is constant or intermittent. It was found that C equi could be recovered from every property tested and from all horse breeds. The organism was found in mares, stallions, yearlings and two year olds, and foals aged from 10 days to several months. It appears that C equi is widespread and that its occurrence is not related to any particular geographical location nor to a limited number of properties within a given area. Furthermore, it seems likely that C equi is part of the normal equine faecal flora. The results challenge the notion that C equi is primarily soil associated and do not support the concept that there are infected and non-infected areas.