An assessment of the methods currently available for the diagnosis of lumpy skin disease, and of pseudo-lumpy skin disease caused by Allerton virus, has been made. With the electron microscope, positive identification of a vaccinia-type virus particle could readily be made within hours of the receipt of the skin biopsy sample. With fluorescent antibody techniques virus antigen could be detected 48 hr. after the inoculation of laud) testis cell cultures. These results have been compared with the existing procedures, which involve the recognition of inclusion bodies in skin sections of lesions and in tissue culture cells.