The relationship of CYP2A6 genotype to nicotine metabolism and smoking intensity (measured by TNE) has been demonstrated in two lung cancer studies.7,13,40 The first was carried out in a Shanghai cohort and examined four variant alleles (CYP2A6*1A, *4, *7, *9, see Fig. 4a) that have a relatively high frequency in Chinese. Here, CYP2A6 is linked to lung cancer.