Self‐mutilation in non‐human mammals is a well‐established, although not a widely known phenomenon, which has been reported under zoo and laboratory conditions. In macaque monkeys, laboratory rearing and isolation are important predisposing factors, and the more serious self‐injury is initiated by some immediate stimulating event. It is commonly accompanied by behaviour normally shown by the animal in a flghting context. Lower mammals are also known to mutilate themselves under laboratory conditions after administration of drugs which probably cause increased sympathetic activity. The implications of this behaviour for an understanding of states of self‐injury in man are discussed.