Fifty-four per cent of 52 patients presenting to the University of Malaya Medical Centre with a myelopathy for which appropriate investigations uncovered no definite etiology, subsequently developed clinically definite or probable multiple sclerosis. In the subgroup of patients with a presentation indicative of acute/subacute transverse myelopathy, 14 or 52% also went on to develop clinically definite or probable multiple sclerosis, a far higher proportion than previously recorded in the literature. This finding is probably a further manifestation of racial difference in the behaviour of multiple sclerosis. For the group as a whole, the only factor which appeared to be associated with an increased risk of developing multiple sclerosis was female sex; 67% of 33 female patients went on to develop multiple sclerosis after a mean follow-up period of 5.5 years. Other factors such as age of onset, racial composition, level of spinal cord involvement, presence of fever and CSF finding were found not to be important.