Isolation of Mortierella wolfii in 5 separate cases of cattle infection is reported. In one case, the fungus was recovered in pure culture from the milk of an animal with mastitis. It was not conclusively established whether M. wolfii was linked to the mastitis or the cow's death, but circumstantial evidence suggests a possible association.ADDITIONAL ABSTRACT:The isolation of M. wolfii from 5 separate cases of infection in cattle is reported. In 3 cases the fungus was implicated as the causative agent of mycotic abortion. In 1 case M. wolfii was isolated from the diseased liver of a calf and in another case from the milk of a cow with acute mastitis.