Sex-related differences in lung cancer pathology (women more often have adenocarcinoma, more women with lung cancers have K-ras mutations, and so on)2,3, lung cancer risk factors (women appear to have an increased risk of cancer at lower levels of tobacco exposure)4–6, natural history (women appear to have cancers with a slower doubling time)5,7, and prognosis (women appear to have better survival with advanced disease)8,9 have led to the examination of sex-specific factors that may be at work in lung cancer. This evidence concerns the gene KRAS and lung carcinoma.