Caseous lymphadenitis is a serius disease or sheep and goats. Sheep from ten villages and one governmental farm in Assiut governorate were examined for clinical manifestation of the disease and the isolation of the causative organism. Sheep from abattoir were also examined before and after slaughter for the same purpose. It was found that the parotid lymph node was the one that showed the highest percentage of infection. Moreover lambs below six months of age were found to be infected, although they were never been shown before. Ingestion was found to be the most predominant route of infection in Upper Egypt. Samples from surface soil of some sheep dwellings, faeces, surface skin and nasal swabs, from both apparently normal and clinically infected sheep failed to yield the Causative organism on culture. By experimental infection it was found that both intra dermal and S/C inoculation only yielded the organism from the inoculation site and failed to isolate the organism by scarification method. Oral dosing was negative to any lesions in case of small dose, However, a bigger dose resulted in enlargement of mesen tric lymph nodes and from which the organism was isolated. Intravenous inoculation produced lesions in parenchymatous organs, from which the organism was isolated.