This open-label, randomized, parallel arm study assessed the efficacy and safety of Tarceva (erlotinib) versus gemcitabine/cisplatin combination chemotherapy as first-line treatment in patients with stage IIIB/IV non-small cell lung cancer with epidermal growth factor receptor (EGFR) mutations in their tumours. Patients were randomized to receive either Tarceva 150 mg orally daily or 3-week cycles of gemcitabine 1250 mg/m^2 intravenously (iv) on Days 1 and 8 plus cisplatin 75 mg/m^2 iv on Day 1.