Erlotinib and gefitinib are quinazoline derivatives that selectively and reversibly inhibit the tyrosine kinase activity of the EGFR. Activating mutations in the EGFR confer hypersensitivity to the tyrosine kinase inhibitors gefitinib and erlotinib in patients with advanced non-small-cell lung cancer. Erlotinib has been developed in EGFR mutation-positive patients as a firstline treatment, and results from recently completed phase III studies have shown superior progression-free survival and response rates for erlotinib, compared to chemotherapy.