In modern medicine the term "functional symptoms" is usually used to refer to symptoms where an organic cause cannot be found. Studies have shown that up to half of all patients consulting their family physician and approximately one third of all those attending neurology outpatient clinics present with such symptoms. These patients commonly go between doctors, repeatedly undergo unnecessary tests, even surgery, and various drugs are tried with limited success. These problems tend to be prolonged and greatly reduce the quality of life for the patients involved. Both the DSM IV and ICD 10 classifications include a group for the so-called medically unexplained disorders. Among these disorders is conversion disorder where patients present with neurological symptoms, affecting motor or sensory function, but with no neurological explanation. Here we provide an overview of the current ideas on the aetiology, diagnosis, treatment and prognosis of conversion disorder.