Ten buffalo-calves were intradermally Inoculated with a strain of C. peseudotubercul osis (ovis), "A Bu 77", isolated fril a case of ulcerative lymphangitis. Skin biops eis were taken at periods of 4,8 and 12 hours after infection. Two animals were slau ghtered after 1,2,4,7 and 15 days. Crossly, changes consisted of oedematous smelling, which extended in some cases to the dewlap, necrosis, and in later stages adhesion of the skin with the underlying muscles. The regional lymph nodes showed congestion and necrosis. Two animals died after 6 and 11 days, the latter showed the clinical pict ure of Jaundice. Microscopically, callulitis with. infiltration of neutrophils in the area, as well as damage and thrombosis of blood and lymph vessels occurred in the skin. This was followed by proliferation of fibrous connective tissue formation. Nec rotic changes were very marked both in early infiltrating neutrophils and lymphoreic ular elements of the lymph nodes. Liver and kidney revealed degenerative changes. Immunofluoresceince examination revealed that the organism occurs intracellularly, most probably in macrophages in skin and lymph nodes, and that it has an affinity to endothelial linning of lymphatics in the skin. Pathological changes induced by this strain were attributed to a powerful cytotoxic effect of an exotoxin.