Observations on the appearance of tissue mast cells in the skin, trachea and various portions of food-passage-tongue, esophagus, stomach, small intestine and large intestine, were made after per oral administration of 25mg. per Kg. body weight and 250 mg. per Kg. body weight of Ginseng extract, with follow-ups after various time intervals, using healthy albino-rats weighing 120-130 gm. each. The following results were obtained ; 1) After the administration of Ginseng extract, the numbers of tissue mast cells in the various tissues examined showed rapid decrease, reaching the minimal levels at the 3 to 4 hours, and gradual increase thereafter to the normal level. 2) The decreasing rates of the numbers of tissue mast cells in various tissues to the minimal levels were approximately 70-80% of the normal groups. 3) The decreased numbers of tissue mast cells in various tissues to the minimal level were gradually increased, reaching to the normal level at 8 hours approximately and then the numbers of tissue mast cells showed slight decreasing trend but recovered to the normal level soon after. 4) There was no significant difference of changes in the appearance of tissue mast cells with the amount of administrated Ginseng extract to the tissue mast cells in various tissues examined. 5) In the morphology of the tissue mast cells after administration of Ginseng extract, the percentage of the normal mast cells decrease and that of the degranulating form of the tissue mast cells increase when the number of tissue mast cells decrease, and thereafter, as the number of mast cells increases, the percentage of the normal form increase and that of the degranulating form decrease, thus reaching the normal state. In general, the time of recovery in the percentage of the normal forms lagged behind that in the number of mast cells in all of the experimental groups.