A 74-year-old-woman who had never smoked was diagnosed in 2004 with cT3N2M1, stage IV primary pulmonary adenocarcinoma. After seven courses of chemotherapy with carboplatin and paclitaxel, she was given gefitinib as second-line therapy and made satisfactory progress. However, gefitinib was discontinued after 3 years of treatment due to re-growth of the tumors. She was then given chemotherapy with docetaxel as a third-line therapy. Over the course of time, meningeal carcinomatosis occurred in conjunction with her previous disease. Upon re-treatment with gefitinib, her meningeal carcinomatosis showed some improvement despite the growing primary tumor, so her QOL was improved. She is now visiting a hospital as an outpatient. When analysis of the EGFR gene mutant was conducted, deletion mutation of E746-A750 in exon 19 was revealed in the 2004 pulmonary tissue, as well as the cytological examination of cerebrospinal fluid and pulmonary tissue after recurrence. No change has been observed. Once gefitinib proved effective, re-treatment with gefitinib was considered useful after its discontinuation.