A review of studies using cholinergic drugs as tools to investigate the neural mechanisms mediating affective and predatory aggressive behaviour reveals that the same two cholinergic systems are involved with both sorts of behaviour. There is a brain muscarinic system initiating aggression and a nicotinic system which inhibits aggressive behaviour. This evidence suggests that there could be two possible forms of cholinergic therapy for aggression, cholinolytics and nicotinic agonists. These possibilities are discussed.