This study investigated whether epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKI) increase the development of leptomeningeal metastasis (LM) compared with standard chemotherapy in EGFR mutation-enriched non- small cell lung cancer. The incidence of LM was longitudinally assessed in never smokers with advanced adenocarcinoma of the lung enrolled in a phase III randomized controlled study that compared gefitinib with gemcitabine plus cisplatin (GP) as first-line therapy (The First-SIGNAL study). Among 203 patients who were enrolled at the National Cancer Center Hospital (Goyang, Republic of Korea), LM occurred in 32 (15.8 %) with a minimum follow-up time of 55.1 months. The 1-, 2-, and 3-year actuarial incidence rates of LM were 5.3, 10.6, and 24.6 %, respectively. During first-line treatment, LM occurred in 2 patients (2.0 %) treated with gefitinib and in 3 patients (3.2 %) treated with GP. There was no difference in the incidence of LM during first-line treatment between the two groups (P = 0.934). The incidence of LM was significantly increased during second-line EGFR-TKI treatment compared with first-line EGFR-TKI treatment (P = 0.041). During the disease course, the cumulative incidence of LM was not significantly different between the two treatment groups (P = 0.514). The median time to LM was 21.4 and 24.0 months in the gefitinib and GP groups, respectively (P = 0.895). Similar trends were observed in the subset analysis with 23 EGFR-mutant patients. In conclusion, LM predominantly occurred in the late phase of disease in this population. EGFR-TKIs did not affect the incidence or timing of LM development.