Events such as the Nuremberg Trials in Germany, or the Truth and Reconciliation Commission proceedings in South Africa, raise questions about the psychology of perpetrators of crimes against humanity. While such violations occur within particular socio-political contexts, given the significant advances in clinical neuroscience in the past several decades, is it possible to outline a 'psychobiology of evil'? In this paper a preliminary approach towards this area of study is made on the basis of a review of the biological psychiatry literature. In particular, this literature is used to draw a distinction between the psychobiology of 'banal' evil and that of 'sadistic' evil. Whereas banal evil may involve a dissociation of cortico-striatal processing from limbic input (reason without passion), sadistic evil may involve a dissociation of limbic processing from frontal controls (passion without reason). A biological perspective on evil must, however, avoid several kinds of reductionism. A non-reductionistic psychobiological perspective may provide new insights into a spectrum of deviant behaviour ranging from everyday peccadilloes to pathological evil.