Neuropsychiatry has a long and fascinating history as a discipline at the interface between neurology and psychiatry that combines clinical observations with modern investigational techniques. Historically, organic psychiatry has focused on clinical syndromes with regional connections affecting the four cortical lobes and the corpus callosum. Behavioural neurology has developed from early observations of classical neurocognitive syndromes, including aphasia, alexia, apraxia, agnosia and Gerstmann syndrome. A number of common neurological conditions often present with specific psychiatric symptoms: traumatic brain injury, cerebrovascular disease, brain tumours, epilepsy, movement disorders, infectious diseases and autoimmune neurological disorders such as multiple sclerosis, systemic lupus erythematosus and autoimmune encephalopathies. The differential diagnosis between delirium, dementia and pseudodementia can pose significant challenges. Finally, several toxic, metabolic and endocrine disorders can have clinically relevant neuropsychiatric manifestations.