In this experiment, observations were made on the effects of ginseng saponin, one of the major components of Korean ginseng (Panax ginseng, C. A. Meyer) root, on the membranes of microorganism (E. coli K-12), the concentration of intracelluar and extracellular cycle AMP therein, and uptake of U-14C-glucose. When the E. coli were grown on media containing 0.1% ginseng saponin, the growth was faster than for that of the control by about 30 minutes. The lysis of E. coli grown on the ginseng saponin medium increased to about double that of the control in the stationary phase. And the amount of protein and lipopolysaccharides in the outer cell meberances increased 25% and 80% respectively in comparison with the control. By electron microscope observation, it was shown that the periplasmic region of the E. coli grown on the ginseng saponin medium was widened it was observed that the cellular cyclic AMP content of the E. coli increased significantly to the hightest levels between the late exponential phase and early stationary phase. The total cyclic AMP content of E. coli grown on the ginseng saponin medium decreased about 50% when compared to that of the control.