The Salter-Harris classification system is widely used to describe the anatomical appearance of and predict the prognosis for physeal fractures in canine clinical patients. Salter and Harris classified experimentally induced physeal fractures on radiographic and histological appearance, however, the good prognosis afforded Salter-Harris type I and II fractures in experimental animals has been questioned for the canine patient. Twelve naturally occurring physeal fractures from five traumatized dogs, who were euthanatized at the request of their owners, and one resected femoral head were examined histologically. Ten of the 13 physeal fractures disrupted the cells in the proliferative zone. The histological appearance of growth plate disruption in the injured animal correlates more closely with the clinical observations of growth retardation than the experimental observation of continued growth after fracture through the hypertrophic zone. The results of this study indicated that considerable damage to the physeal cartilage occurred during the traumatic incident in most of these clinical animal patients.