Metastatic breast cancer is still defined as an incurable disease, with the lungs being the most common metastatic sites in breast cancer patients. Epidermal growth factor receptor (EGFR), a member of receptor tyrosine kinase family, is known to be involved in survival, migration, angiogenesis and metastasis of cancer. The spontaneous pulmonary metastasis mouse model was applied to evaluate the effects of the EGFR tyrosine kinase inhibitor, erlotinib, on the prevention of pulmonary metastasis in curatively resected breast carcinoma. The expression of EGF and EGFR was significantly strong in pulmonary metastatic nodules compared to those in primary breast carcinoma tissue. A treatment of erlotinib (oral gavage, 50 mg/kg/day, every day for 6 weeks) given to mastectomized mice inhibited the incidence of pulmonary metastasis. The number of metastatic pulmonary nodules was significantly reduced in the erlotinib-treated group compared with the control. Therefore, erlotinib may play a role in preventing pulmonary metastasis, which shows the strong expression of EGF and EGFR after curative resection of primary breast cancer.