There is no subject at the interface of law, psychiatry and medical ethics which is more controversial than psychosurgery. The divergent views of the treatment begin with its definition. The World Health Organisation1 and others2 define psychosurgery as the selective surgical removal or destruction of nerve pathways or normal brain tissue with a view to influencing behaviour. However, proponents of psychosurgery demur on the basis that the `modern' treatment is concerned predominantly with emotional illness, without any specific effect upon behaviour. (...) The alternative definition offered is `the surgical treatment of certain psychiatric illnesses by means of localised lesions placed in specific cerebral sites.3It is difficult entirely to accept this definition because, as examined below, scientific psychiatry is not yet in a position to directly treat psychiatric illness solely through surgical intervention. There is no reliable theoretical relationship between particular cerebral sites (which are normal and healthy) and an identifiable psychiatric illness or symptomatology. Given this state of psychiatric understanding, it is misleading to suggest fine distinctions between generalised alteration of behaviour or mood and treatment of an illness. Highly divergent practices and theories (relating to the multiplicity of conditions treated, surgical methods adopted and areas of the brain operated upon) further undermine exaggerated claims that psychosurgery can scientifically `treat' specific illness through precise surgical intervention. Nonetheless, contemporary psychosurgery does not contain quite the same `broadbrush' approach of its ancestors and it can lay some legitimate claim as an effective empirical treatment in narrowly limited circumstances. Major ethical problems still, however, arise and these will be discussed in this article. (shrink)