Methanol extracts of Acorus gramineus Solander(AGS) were found to exhibit immuno-regulatory action in BALB/c mice. Oral administration of AGS increased murine splenic T lymphocytes, especially $T_H$ and $T_C/T_S$ subpopulations were increased significantly. Treatment of AGS exerted strong cytotoxicity against U937 and HL60 human leukemia cells. Also, AGS induced apoptosis of U937 leukemia cells in a dose dependent manner. Nitric oxide(NO) production and iNOS gene expression were also increased in AGS-treated RAW264.7 cells. Treatment of AGS increased the expression of p53 gene and decreased the expression of PCNA protein in cultured U937 cells. These data suggest that AGS are effective on the immuno-regulatory action and anti-cancer properties.