Objective: This Study was to investigate effects of Neasookseul-Tang on the anti-cancer, proliferation of immunocytes and nitric oxide(NO) production of peritoneal macrophages. Methods: We used Neasookseul-Tang extract(NOT) with freeze-dried, 8wks-old male mice(balb/c, ICR) and cancer cell lines(L1210, sarcoma-180) for this Study. The proliferation of cells was tested using a colorimetric tetrazoliun assay(MTT assay). Results: 1. NOT was significantly showed cytotoxicity on the L1210 and Sarcoma-180 cell lines. 2. NOT was significantly increased proliferation of thymocytes and splenocytes in vitro. 3. NOT was significantly decreased proliferation of L1210 cells in L1210 cells transplanted mice. 4. NOT was significantly increased proliferation of thymocytes and splenocytes in L1210 cells transplanted mice. 5. NOT was significantly increased NO production from peritoneal macrophages in L1210 cells transplanted mice. 6. NOT was significantly inhibited body weight and tumor weight in Sarcoma-180 cells transplanted mice. 7. NOT was significantly increased in the mean survival days in Sarcoma-180 cells transplanted mice. Conclusions: The present author thought that NOT had action of anti-cancer by accelerating immuno-function.