The ability to infer other persons' mental states and emotions has been termed 'theory of mind'. It represents an evolved psychological capacity most highly developed in humans. The evolutionary origins of theory of mind can be traced back in extant non-human primates; theory of mind probably emerged as an adaptive response to increasingly complex primate social interaction. This sophisticated 'metacognitive' ability comes, however, at an evolutionary cost, reflected in a broad spectrum of psychopathological conditions. Extensive research into autistic spectrum disorders has revealed that theory of mind may be selectively impaired, leaving other cognitive faculties intact. Recent studies have shown that observed deficits in theory of mind task performance are part of a broad range of symptoms in schizophrenia, bipolar affective disorder, some forms of dementia, 'psychopathy' and in other psychiatric disorders. This article reviews the evolutionary psychology of theory of mind including its ontogeny and representation in the central nervous system, and studies of theory of mind in psychopathological conditions.