Objective: To assess the efficacy and toxicity of gefitinib as a single agent treatment in Chinese patients with advanced non-small cell lung cancer (NSCLC). Methods: Forty-five patients with advanced NSCLC were treated with gefitinib at 250 mg daily until the disease progressed or the patient could not tolerate the toxicity. Results: None of the patients achieved a complete response (CR), while 15 patients achieved a partial remission (PR) and 17 experienced a stable disease (SD). Thirteen patients continued to have a progressive disease (PD). The response rate and the disease control rate were 33.3% and 71.1%, respectively. The symptom remission rate was 72.5%, and the median remission time was 8 days. The median survival time was 15.3 months. The median progression-free survival time was 6.0 months. The most common toxicities included rash (53.3%) and diarrhea (33.3%). Dehydration and pruritus of the skin developed in 26.7% and 22.2% of the patients, respectively. Hepatic toxicity occurred in 6.7% of patients and oral ulceration occurred in 4.4% of patients. Conclusion: Single agent treatment with gefitinib is effective against advanced NSCLC, and is well tolerated in Chinese patients.