Erlotinib (Tarceva, previously known as OSI-774) is an orally active, potent, selective inhibitor of the Epidermal Growth Factor Receptor (EGFR) tyrosine kinase. A recently completed trial has shown that Erlotinib as a single agent significantly improves the survival of patients with incurable Stage IIIb/IV NSCLC who have failed standard therapy for advanced or metastatic disease. Therefore, Erlotinib is an approved medication for second-line therapy in lung cancer following prior chemotherapy.