Multiple sclerosis (MS) may occur outside the commonly accepted age range. Data relating to features of MS in a population in South Wales have been analysed to find features which characterise older patients. The older patients are more severely disabled due to the accumulation of visual defects and motor signs and symptoms. The course of the disease is marked by single localised attacks with long remissions. Those with onset over 50 years deteriorate more rapidly, but in those who were over 50 at the time of interview, this did not occur. It is suggested that there is no essential difference in MS in older patients, but there may be features which reflect normal ageing and diseases commoner in old age.