Twenty-four cases of an acute ophthalmia of cattle have been observed. The infection is characterized by photophobia, severe congestion of the vessels of the eyeball, conjunctivitis, congestion and edema of the membrana nictitans, edema of the eyelids, accompanied by a thick, yellowish white mucus or mucopurulent exudate. In certain cases corneal ulcers and extensive corneal opacities developed. From all cases a characteristic diplobacillus was obtained. The organism was usually observed in the exudate in large numbers. The morphology, the hemolytic properties, and the proteolytic activities readily assist in its identification. Instillation of a few drops of bouillon suspensions of pure cultures beneath the eyelids of normal cattle gave rise to characteristic inflammations. The organism is not pathogenic for laboratory animals.