Methods: The matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectroscopy-based genotyping system was used to genotype 601 individuals (200 lung cancer patients and 401 age- and sex-matched healthy controls) for polymorphisms in excision repair cross-complementing group 1 (ERCC1) and ERCC5 genes. The gene discussed is ERCC1; the disease is lung cancer.