Intensive search over the past five years for all cases of multiple sclerosis (MS) on the Faroe Island since about 1920 has revealed 25 cases among native-born resident Faroese up to 1977. All but 1 patient had clinical onset of MS between 1943 and 1960; 1 case began in 1970. Four cases of MS in Faroese with prolonged foreign residence and 5 among Danish-born Faroese were excluded. The 24 included cases with onset between 1943 and 1960 meet all criteria for a point-source epidemic. The median year of onset was 1949. The cumulative risk of MS for Faroese in 1940 was 8.7 per 10,000. All 14 early-onset cases (1943 to 1949) were in patients 11 to 45 years old in 1940; all but 2 late-onset cases (1952 to 1960) were in persons aged up to 10 years old in 1940. British troops occupied the Faroese in large numbers for five years beginning in April, 1940. During the war, all but 3 patients resided in locations where the troops were stationed, and these 3 also had direct contact with the British. We conclude that there was an epidemic of MS on the Faroes and that the disease was probably introduced by the British troops (or their baggage). If so, then MS on the Faroes is a transmissible disease, most likely infectious; but only about 1 in 500 of the exposed individuals were clinically affected.