Corynebacterium pseudotuberculosis is a bacterial agent responsible for CLA in ruminants and the three manifestations of ulcerative lymphangitis, external abscesses, and internal abscesses in horses. This paper summarizes a typical case of pigeon fever (external abscesses) in a 14 year old quarter horse mare presenting with pectoral swelling and ventral edema. Although her abscess matured and ruptured within a week with the minimal intervention of NSAID treatment, hot packing, and fly control, some cases may require ultrasonography and lancing to establish drainage. Rare complications such as systemic clinical signs, purpura hemorrhagica, and even mortality can occur when the disease disseminates internally to establish internal abscesses. Although pigeon fever is geographically restriced to western USA, it is spreading to more humid and eastern states such as Colorao, Utah, and even Kentucky and Florida. Currenlty one of the most prevalent bacterial infectious disesases of the horse, even equine veterinarians practicing in eastern United States will benefit from further investigation of the pathogenesis, transmission, and development of a possible vaccine for the disease.