Antitumor activity of Korean mistletoe extract (KM-110) and European commercial mistletoe preparation (Helixor) was investigated. KM-110 showed the cytotoxic effect that it is high for various tumor cell lines and normal splenocytes in comparison with Helixor. Administration of two mistletoe extracts ($100{mu}g$) to mice did not show any significant changes on the level of glutamic-oxaloacetic transaminase (GOT), glutamic-pyruvate transaminase (GTP), blood creatinine (CRE) and blood urea nitrogen (BUN) in sera. The culture supernatant of macrophages stimulated with KM-110 inhibited effectively tumor growth whereas Helixor had little effect. Administration of KM-110 or Helixor resulted in a effective inhibition of lung metastasis after the i.v. inoculation of colon 26-M3.1 lung carcinoma, B16-BL6 melanoma and L5178Y-ML25 lymphomas. In all cases, the mice treated with KM-110 showed more effective anti-tumor metastatic activity than the mice of Helixor. These results suggest that Korean mistletoe extracts, KM-110 might be used as an alternative methods having antitumor activity like European mistletoe preparation, Helixor.