M. F., a white man aged 35, had worked as a chauffeur and a telephone lineman previous to his present occupation as a fireman. He was referred to us in 1930 by the Chicago Fire Department as a suspect malingerer because of his complaint of asthma after each fire. His past history was negative except for scarlet fever during childhood. No history of atopy was obtainable either in him or in his family. He had never previously had respiratory symptoms. The Chicago Fire Department informed us that there are 2,795 men employed in Chicago as firemen and that about 20,000 fires occur every year. This was the first case of asthma the department had observed that was attributable to smoke. During the first eight months of his work as a fireman he had been to about 250 fires. Some of these were associated with severe smoke exposure, without, however, any