Over twenty years ago, London et al. reported that the presence of inactivating CYP2D6 alleles (CYP2D6*4, CYP2D6*3, CYP2D6*5, and CYP2D6*16) may decrease the risk of lung cancer among the African-Americans, suggesting the CYP2D6 genetic polymorphism is not the strong risk factor for lung cancer but may play a minor role (London et al., 1997). This evidence concerns the gene CYP2D6 and lung cancer.