Infection with Actinobacillus lignieresi is found frequently in the bovine here in the Middle West. Too frequently the term actinomycosis is used to include those lesions of both the soft tissues and bones of the head and mandible. As a general rule, we find actinobacillosis involving the soft tissue with Actinomyces bovis invading the bony tissue. Actinobacillosis is found most frequently in the region of the head but may become rather generalized involving almost any tissue of the body. Whenever an actinobacillosis abscess is opened the pus is very characteristic as it is nonodorous, very thick and tenacious, may be white or with a slightly yellowish tinge and containing a variable quantity of mucus.