From September 2008 to April 2009, we have analyzed patients with histologically confirmed NSCLC for the presence of mutations in exons 18–21 of EGFR and exons 2 and 3 of KRAS. Patients enrolled in this mutation analysis study are not representative for the prevalence of such mutations in NSCLC as they were enriched for cases with an increased likelihood of being EGFR mutation-positive based on histological and clinical features (e.g., lung adenocarcinoma in never or light ex-smokers). The gene discussed is EGFR; the disease is lung adenocarcinoma.