OBJECTIVE : To study the clinical significance of serum epidermal growth factor receptor (EGFR) gene mutation and serum tumor markers in the prediction of tyrosine kinase inhibitor (TKI) efficacy in patients with lung adenocarcinoma. METHODS : Ninety patients with pathologically diagnosed lung adenocarcinoma were enrolled. Further, 51 out of 90 patients received the EGFR-TKI therapy, oral gefitinib. The correlations among serum EGFR gene mutations in exons 18-21, serum tumor markers such as carcinoembryonic antigen (CEA), carbohydrate antigen 24-2 (CA24-2), carbohydrate antigen 125, carbohydrate antigen 15-3 as well as carbohydrate antigen 19-9 (CA19-9) levels, and EGFR-TKI efficacy were determined. RESULTS : There was a high consistency of EGFR gene mutation rate between serum and tissue samples. The serum EGFR gene mutation rate in female patients or non-smokers was significantly higher than that in male patients or smokers, respectively. Serum CA19-9, CA24-2, and CEA levels were significantly correlated with serum EGFR mutation. After receiving gefitinib, the progression-free survivals (PFSs) of patients with high serum CEA level, high serum CA19-9 level, or serum EGFR gene mutation were significantly higher than those of normal patients, respectively. The PFSs were significantly prolonged in patients with EGFR gene mutation and high serum CEA level or patients with EGFR gene mutation and high serum CA19-9 level compared with those in patients with one abnormal biomarker and normal patients. CONCLUSIONS : Combined detection of EGFR gene mutations as well as CA19-9 and CEA levels in peripheral blood can predict the efficacy of EGFR-TKI in the treatment of patients with lung adenocarcinoma.