The observation that exposure to BPDE (a smoke constituent) induces G:C → T:A transversions has predominantly been reported for the p53 tumour suppressor gene in lung cancer (Hussain et al, 2001) and may not apply to all genes and cancer sites, for example, not one p53 G:C → T:A transversion was observed in smokers in a study on bladder cancer (Spruck et al, 1993). The gene discussed is TP53; the disease is urinary bladder carcinoma.