Clinical onset of multiple sclerosis (MS) occurred in 32 native resident Faroese between 1943 and 1973, comprising 3 consecutive epidemics of decreasing frequency. Relationship of MS with the appearance of canine distemper (CD) was explored by serologic studies, questionnaires, and veterinarian reports. Tested were sera from 12 MS patients and 112 controls among the 22 patients and 192 controls with questionnaires in 1978-1979. The daily treatment ledgers of the Veterinarian of the Faroes 1940-1961 were also reviewed and additional Faroese interviewed 1987-1988 as to CD. History of CD was determined for residence of all 32 MS. There was no evidence of elevated CD antibody titers in MS vs controls for neutralizing titers or ELISA values, nor to ELISA for measles. In the questionnaires only one patient and 2 of his sibs reported owning (the same) dog(s) with CD during the war. One other patient reported a possibly sick dog but not CD. CD occurred in one southern village 1941-1942, was present on Vágar from 1941-1950, and was epidemic on Streymoy 1944-1945 with scattered cases there and elsewhere through 1950. There was no significant correlation between villages with CD and MS residents. We conclude that the occurrence of multiple sclerosis was not related to the presence of canine distemper or sick dogs in the Faroe Islands.