Big head is an acute, infectious disease caused by Clostridium novyi, C sordellii, or rarely C chauvoei, characterized by a nongaseous, nonhemorrhagic, edematous swelling of the head, face, and neck of young rams. This infection is initiated in young rams by fighting or continual butting of one another. It has also been associated with the practice of dipping immediately after shearing. The bruised and battered subcutaneous tissues provide conditions suitable for growth of pathogenic clostridia, and the breaks in the skin offer an opportunity for their entrance. Treatment is with parenteral administration of broad-spectrum antimicrobials or penicillin.