Objectives: The purpose of this study is reporting the possibility of the treatment of metastatic brain tumors with allergen removed Rhus verniciflua Stokes (aRVS) after gamma knife radiosurgery. Methods: A patient with lung cancer felt a headache about one year after conventional therapies, and metastatic brain tumors were diagnosed. He received gamma knife radiosurgery twice but refused to get more conventional therapies afterwards. So he has been treating with aRVS since then. Results: During 143 weeks of administration of aRVS, the size of brain masses has decreased continuously without extracranial metastasis and the patient has maintained a good performance status. Conclusions: This report suggests that aRVS may play a therapeutic role in the treatment of metastatic brain tumors. Further studies will be needed to determine the effect of aRVS on metastatic brain tumors.