A controlled serologic survey of antibody titres to 17 viruses was undertaken in multiple sclerosis patients in the Orkney and Shetland Islands. No consistent pattern of elevated antibody titre levels or the presence of antibody was noted in patients compared with two control groups. Because of the isolation of these islands, the mean age at acquisition of common childhood infections, including measles, was considerably older than that of inhabitants of Europe and the United States of America. The age of occurrence of varicella was consistently younger in patients than in controls. Of note is the fact that six patients had measles after the onset of MS. This study failed to incriminate any of the viruses tested in the aetiology of MS.