The multinational, multi-institutional clinical Phase II trial of gefitinib monotherapy, IDEAL (IRESSA Dose Evaluation in Advanced Lung Cancer) 1, included Japanese and non-Japanese patients with advanced non-small-cell lung cancer (NSCLC) pretreated with one or more chemotherapy regimens, at least one including platinum. To investigate whether survival is affected by gender or histological type of cancer, a retrospective, exploratory subset analysis was conducted including only Japanese patients from IDEAL 1 (n = 102 in total, 51 each in 250 and 500 mg/day groups). The median survival time of the 102 patients was 12.0 months and the one year survival rate was 50%. The median survival time was 13.8 months for the 250 mg/day group and 11.2 months for the 500 mg/day group and the one-year survival rate was 57% and 45% respectively. Survival was longer in patients with adenocarcinoma than those with other histological types of cancer, and was longer in those with symptom improvement than without. The median survival time in females was longer than that in males. The results suggest that gefitinib could be superior to classical anticancer agents with regard to not only the response rate but also survival time in patients with NSCLC, particularly adenocarcinoma, previously treated with chemotherapy. Further studies are needed to identify factors affecting survival.