In a defined population of 112,000, an attempt was made to discover every patient with multiple sclerosis. Using strict diagnostic criteria, 91 patients were identified. A search of psychiatric records for the same population revealed that 15 (16%) of these patients were referred to psychiatrists between the onset of their symptoms and the diagnosis of multiple sclerosis. Ten (11%) were seen with symptoms attributable to multiple sclerosis. These symptoms were recognized as neurological in only two cases, while the other eight patients received a variety of psychiatric diagnoses. Possible reasons for diagnostic error included the subjective nature of many early symptoms, histrionic behaviour, and psychiatric disturbance which drew attention away from physical symptoms. The results underline the caution needed when patients with physical symptoms are referred for psychiatric assessment.