Treatment outcome for advanced-stage non-small cell lung cancer (NSCLC) is limited by empiric administration of cytotoxic chemotherapy. Recent advances in molecular genomics have revolutionized cancer management and, specifically, epidermal growth factor receptor (EGFR) mutation has become a potent biomarker for lung cancer, which predicts tumor response to and prolonged duration of disease control by EGFR tyrosine kinase inhibitors (TKI). The Iressa Pan-Asia Study (IPASS) is a randomized phase III study comparing gefitinib (EGFR TKI) with paclitaxel/carboplatin (standard chemotherapy) in Asian non-/light smokers with adenocarcinoma. Progression-free survival (PFS) in EGFR mutation-positive patients was longer with gefitinib than with chemotherapy (hazard ratio [HR], 0.48; 95% confidence interval [CI], 0.36-0.64; p<0.0001); in EGFR mutation-negative patients, PFS was longer with chemotherapy than with gefitinib (HR 2.85; 95% CI 2.05-3.98; p<0.0001). The findings are confirmed by one single-arm study and three other randomized studies. It has become clear that personalized medicine for NSCLC is feasible. This small step towards personalized medicine represents a paradigm shift in the management of NSCLC.