Adenoviral infection was established in imported specialized meat strains of sheep Ile de France and Romni marsh. The disease followed a course typical of chronic interstitial progressive pneumonia with reduced tonus, loss of body weight, and high lethality. The disease was serologically proven by the discovery of specific complement binding antibodies in dynamics against the adenovirus. Titers varied from 1 : 2 to 1 : 32. The infestation was reproduced on sheep and lambs by tracheal infection with ultrafiltrate of changed lung tissue and bronchial lymph nodes. Morphologically the infection manifests itself by considerable hypeplastic processes in the lungs and less pronounced ones in the liver and kidneys. The typical changes indicated are accumulation of lymphoid cells and histocytes in the interstitial tissue, as well as adenomatous expansion of alveolar and bronchial epithelium. Considerable cell polymorphism is observed in the alveoles along with presence of gigantic cells and cell syncytia of desquamous epithelial cells, alveolar macrophages and intranuclear inclusions in some of these cells. Complications of Past. Haemolytica with developing catharalsuppurative pneumonia were observed in some cases.