Somatic mutations in the epidermal growth factor receptor (EGFR) result in enhanced receptor signaling, predicting sensitivity to EGFR tyrosine kinase inhibitors (TKIs), such as erlotinib and gefitinib, in subsets of patients with lung adenocarcinoma (Lynch et al, 2004; Paez et al, 2004; Pao et al, 2004). The gene discussed is EGFR; the disease is lung adenocarcinoma.