The topic of my contribution published recently in a ‘Discussion Forum’ in Mutagenesis was the comparison of different versions of the IARC p53 database with respect to data on lung cancer of smokers and non-smokers. Most importantly, this comparison revealed a number of discrepancies in the classification of smoking status of identical lung cancer entries in different versions (R1, R2 and R3) of the database. Additionally, no statistically significant differences in G→T transversion mutation frequencies or in mutational hotspots at codons 157, 248 and 273 were found in the R3 version of the database comparing lung cancer in smokers and non-smokers. Finally, a possible influence of confounding factors on p53 mutation spectra was demonstrated. In the present Letter Hainaut et al. refer to my paper and conclude that ‘indiscriminate inclusion of mutations in his dataset may partially explain what he sees as discrepancies’. I appreciate the editors of Mutagenesis giving me the opportunity to reply to some critical comments made by Hainaut et al.