This is a randomized, open label, parallel group, multi-centre, phase II study of progression free survival, comparing oral ZD1839 (IRESSA™) (250 mg tablet once daily) to vinorelbine 30 mg/m2 infusion on days 1 and 8 of a 21-day cycle) in chemonaïve, elderly patients with locally advanced (stage IIIB) or metastatic (stage IV) non-small cell lung cancer.