An 83-year-old(at the time of postoperative recurrence)female clinically diagnosed with primary lung cancer underwent right upper lobectomy and lymph node dissection(ND2a-2). Postoperative pathological staging revealed a Stage ⅠB (pT2aN0M0)adenocarcinoma that was EGFR mutation-positive(exon 21: L858R). Fifty-one months after surgery, the patient developed a mediastinal lymph node metastasis, and radiotherapy was delivered. Next, gefitinib(250 mg daily)was prescribed as first-line therapy. She developed mild anemia but we took a wait-and-see approach. A complete response was evident after 58 months of monotherapy. However, she then developed grade 3 anemia(Hb 6.2 g/dL)and gefitinib was discontinued. She requested(and received)follow-up computed tomography. No progressive disease was evident, but she died of non-cancer disease 16 months after discontinuation of gefitinib(thus 125 months after surgery and 74 months after the postoperative recurrence). Thus, we here present an unusual case. Gefitinib monotherapy afforded long-term survival of an octogenarian patient with a postoperative recurrence of a pulmonary adenocarcinoma.