A histological investigation was carried out of the periodontia of young and mature sheep obtained from areas where a periodontal syndrome is endemic in sheep flocks. Observations of the incisor periodontia, which are most commonly affected by the syndrome, revealed no evidence of degenerative or pathological changes of alveolar bone, periodontal ligament or cementum compared with the periodontia of control animals. Minor inflammatory changes of the gingivae, associated with small amounts of a filamentous-type dental plaque, were noted in young animals from areas where the disease is endemic. In mature animals moderate to severe inflammatory periodontal disease with deep pocketing was evident together with dental plaque in the sheep from periodontal disease-prone areas; whereas control specimens showed minimal inflammatory response and dental plaque. It was concluded that periodontal disease in sheep can be described as a localized inflammatory disease initially of the gingivae and later of the deeper periodontal disease.