Using strict diagnostic criteria, 91 patients with multiple sclerosis (MS) were identified in a defined population of 112000. Of these patients, 29 were found to have been referred to a psychiatrist at least once. Their psychiatric records were searched for cases of MS presenting as a pure psychiatric disorder. Only 18 of the 30 psychiatric referrals before the diagnosis of MS involved purely mental symptoms, and there was no reason to suppose most of them to be related to MS. This study highlighted the problem of how to define a true psychiatric presentation of MS. The uncovering of two likely candidates among a population-based sample of 91 supported the existence of such a phenomenon, but it was concluded that the only way to ascertain how often purely mental symptoms might be the first manifestation of MS would be to conduct a large population-based study with controls.