Abstract: Objective: To evaluate the efficacy of sequential administration of gefitinib(Iressa) following a response to two to three cycles of chemotherapy in patients with advanced non-small-cell lung cancer (NSCLC). Methods: Thirty-three consecutive patients with advanced NSCLC pretreated with chemotherapeutic regimens, whose response to the last chemotherapy regimen was confirmed as at least a minor response (MR), entered the trial from May 2002 to February 2005. Patients received 250 mg oral dose of gefitinib once daily for 4 weeks. Treatment was repeated every 4 weeks until disease progression. Results : Thirty-three patients were applicable for evaluation of the response and toxicity. Objective response rate was 24.2% (8 of 33) (95% confidence interval CI, 12.3% to 30.3%). Symptom improvement rate was 54.5% (18 of 33) (95% CI, 25% to 59%). The median time to disease progression (TTP) was 6.5 months. The median overall survival time (05) was 9.8 months, and the actuarial 1-year survival rate was 36.4%(95% CI, 20% to 55%). Toxicity was relatively mild, and only one patient (3.0%) had grade 4 diarrhea, grade 3 nausea and vomiting. Conclusion : Sequential administration of gefitinib following a response to chemotherapy was better tolerated and could maintain and even enhance the effect of previous chemotherapy for advanced NSCLC.