Gefitinib has a modest activity in previously treated patients with advanced non-small cell lung cancer (NSCLC). However, the efficacy and safety of gefitinib monotherapy in untreated advanced NSCLC is not known. We retrospectively reviewed the records of 12 patients of NSCLC who were unfit or refused cytotoxic chemotherapy, and were treated with a single-agent gefitinib as first-line therapy in our hospital. The patients were 6 males and 6 females. The median age was 76.5 years (range 34-82). The histological types were adenocarcinoma in all patients. Clinical stage was IIB in one patient, IIIB in four, and IV in seven. Five were elderly patients and four were patients with ECOG PS (performance status) 3. Five had partial response (PR), and two had stable disease (SD). The response rate was 41%. The median time to progression (TTP) was 126 days. Grade 1 diarrhea was observed in three patients, grade 1 or 2 eruption paronychia was in eight, and grade 1 or 2 liver dysfunction was in two. No grade 3 or 4 toxicities occurred. Gefitinib monotherapy may provide an opportunity for untreated NSCLC, particularly unsuitable patients with standard chemotherapy. Prospective studies of gefitinib monotherapy as first-line treatment are warranted.