Serial determimation of plasma FFA with ginseng extract and propranolol admnistered to experimental animal was done as a pilot study to investigate the mechanism of action of ginseng. The following results were obtained. 1. Intravenous dripping of propranolol 0.5ug/kg/hr result in slight initial elevation of plasma FFA with moderate decrease in later half. 2. Ginseng extract 40mg/kg as a bolus, administered after 2 hour's pre-treatment with propranolol result in moderate initial elevation and slight terminal decrease. 3. Ginseng extract administered concomittently with start of propranolol infusion produced similar change observed with propranolol alone with greater degree. 4. The pilot study suggest the possibility of propranolol acting on the ginseng induced FFA change and raise the question whether the short term ginseng administration can cause significant change of plasma FFA level in experimental animal.