The effects of water extracts and powder of Korean ginseng on the division of Saccharomyces cerevisiae were studied. 1. The addition of several doses of water extracts and powder of ginseng to the yeast medium of Moyer and Coghill showed various promoted division of Saccharomyces. 2. The optimal dose of ginseng on tile division of Saccharomyces (0.08% dry ginseng medium solution per 10 cells/mm³) could be recognized. 3. On the culture for 24 hours at 18℃, the cell number of control group was 13.25 X 10³ cells/mm³ and that of the optimal dose group of water extracts of ginseng was 23.20 X 10³ cells/mm³. On the culture, for 24 hours at 25℃, the cell number of control group was 16.85 X 10³ cells/mm³ and that of the optimal dose group was 30.20 X 10³ cells/mm³. The increasing rate of cell divison by the ginseng was about twice than that of control group. The optimal dose treatment of ginseng at 18℃ was more effective than control group at 25℃. 4. On the culture for 24 hours at 18℃, the increasing rate of water extracts of ginseng was 75.1%, and the rate of ginseng powder was 7.6%. On the culture for 24 hours at 25℃, the rate of water extracts of ginseng was 79.8%, and the rate of ginseng powder was 57.2%. Therefore water extracts of ginseng was more effective than ginseng powder of same dry weight, and the promoted effect of ginseng powder at 25℃ was more effective than at 18℃.