Sensitivity to an inhibitor of epidermal growth factor receptor (EGFR) kinase strongly correlates with EGFR somatic mutations in non-small cell lung cancer. These mutations are frequently found in patients with adenocarcinoma, never- or light-smokers, women, and East Asians. In this study, we show an aggregation of three non-small cell lung cancer cases with EGFR gene mutations in one family. The subjects were all female, never- or light-smokers with adenocarcinoma. Two of the patients responded to treatment with gefitimb. A genetic study of these cases would be useful in elucidating genetic susceptibility to lung cancer in persons with EGFR mutations.