Bronchogenic Carcinoma of the lung in Europeans is now a common disease, whilst it is rare in the Bantu races of South Africa. The writer has been associated with the Silicosis Medical Bureau for the past fifteen years and has checked up all the records since the inception of the Bureau in August 1916. Nearly every miner, even if he leaves the mines, has a post -mortem examination and the lungs are forwarded from all parts of the Union of South Africa to the Bureau for examination. As the Chairman of the Silicosis Medical Bureau writes in the 1944 -1948 Report:- "Under the Silicosis Act it is in the interests of the dependents of a miner that an autopsy should be performed on his death and the lungs forwarded to the Bureau for examination. There are indeed very few cases in which no post-mortem examination is conducted." A full definition of the Bantu races will be given in the Chapter on "History and Anthropology" when it will be noted that they include all the Native tribes of Southern Africa with the exception of the Hottentots and Bushmen. In South Africa, they are also referred to as "Africans, Natives or Kaffirs ". The arguments used in this thesis are mainly based on the clinical histories and post-mortem findings in 6 Bantu cases of "Primary Carcinoma of the Lung" in 11,365 post-mortems of Bantu miners as compared to 114 cases of "Bronchial Carcinoma" in 8,468 post-mortems of European miners, all conducted during the period 1916 -1949. Bronchial Carcinoma is also uncommon in Bantus who are not miners. Amongst the Bantu miners during the period 1925- 1933, Charles Berman (8) found 229 cases of "Primary Carcinoma of the Liver ". The same group of Bantu miners show a high incidence of "Primary Carcinoma of the Liver" and a low incidence of "Primary Carcinoma of the Lung". In this thesis, an attempt will be made to discuss the aetiology of "Primary Cancer of the Lung ", mainly from an anthropathological viewpoint and to try and explain why in a city like Johannesburg, where in terms of the international recommendations, accurate statistics are kept by the health authorities, primary cancer of the lung is about ten times as common in the European as it is in the Bantu.