The Public Health Service is deeply concerned with the increasing death rate from lung cancer in the United States and in other parts of the world. Cancer of the lung is increasing more rapidly and causing more deaths than any other form of cancer in the adult male population. In the United States, the death rate from lung cancer among white men (age-adjusted) was 3.8 per 100,000 population in 1930; by 1956, the rate had risen to 31.0,1and more than 29,000 persons died of lung cancer in that year (fig. 1, table 1). A rising death rate of this magnitude arrests the attention of every physician, private practitioner and public health officer alike. Many investigators have indicted cigarette smoking as responsible in large part for the increasing lung cancer death rate. Others have denied this, saying that increased volumes of automobile exhaust fumes and industrial vapors polluting the