The present study was performed to evaluate the cytotoxicity of white and red ginseng extracts against cancer cells in vitro. We also examined the effects of those ginseng extracts on the cell cycle by using flow cytometry. We divided each white and red ginseng into two parts, main body and rhizome, and tested the cytotoxicity of each fraction against various mouse-originated cancer cells and mouse peritoneal macrophages. The red ginseng was more cytotoxic to the cancer cells in comparison with white ginseng, and the rhizome fractions were more cytotoxic than the mainbody fractions in the both of white and red ginseng. Among the cells tested, RAW264.7 cancer cells were most sensitive to all the ginseng fractions. In cell cycle analysis, all the fractions of white and red ginseng arrested the cell cycle at G$_2$/M phase.