The authors set up a database of 105 genes potentially related to lung cancer susceptibility and 464 of their polymorphisms. The database is based on extensive literature searches, and includes genes likely to influence the internal dose of genotoxic compounds that reach the lungs, following exposure to environmental insults, such as tobacco smoke. The authors selected a subset of 250 single-nucleotide polymorphisms with appreciable frequency in at least one major ethnic group and/or a clear functional role, which represent the best candidates as lung cancer risk factors. They developed a microarray for genotyping these polymorphisms, based on arrayed primer extension (APEX).