The use of convalescent or adult serum in the prevention of measles has been known so long that recent reports serve largely to corroborate previous investigations. Fleming1 has recently reported an epidemic of measles in a school of 300 boys, in which treatment by adult serum was employed. The term started on January 15, and on January 17 a boy was admitted to the school sanatorium with measles; by February 14 serum was given to all who were susceptible. In the end, seventy of the eighty-five patients with measles were treated with serum. They fell into three groups: 1. To fifteen patients serum was not given; they included the original case and one boy who was reported to have had measles as a child. The average period of fever for this group was 8.2 days. Complications included one severe case of bronchopneumonia and two cases of middle ear infection.