Epidermal growth factor receptor (EGFR) plays an essential role in normal cell growth and differentiation, and is involved in tumour proliferation and survival. EGFR overexpression is a common feature in solid malignancies, including non-small-cell lung cancer (NSCLC), and is associated with poor clinical prognosis. Erlotinib is a small-molecule inhibitor of EGFR tyrosine kinase, showing a significant improvement in median survival, quality of life and related symptoms in an unselected population of advanced NSCLC patients in the second- or third-line setting. Erlotinib is well tolerated (with common toxicities including rash and diarrhoea) when administered at a standard oral daily dose of 150 mg. Further investigations are ongoing to contribute to our understanding of the role of erlotinib in NSCLC treatment.