This is to report the observations made on the tissue mast cells in the esophagus, the stomach, and the small and large intestines after feeding 30 mili grams of red pepper daily as a single dose or repeatedly to albino rats weighing 120 to 130 grams. The date are summarized bellow. 1) The esophagus showed the total mast cell count of 21.7±2.97 in 20 high power fields. Of these, the normal form was 89.8% with moderate degranulation, 7.8%, with marked degranulation, 2.3% respectively. 2) The count made on the Transverse section through the mid-portion the lesser and the greater curvatures of the stomach revealed the total count to be 30.0±2.73 and of these the normal form comprised 92.6%, with moderate degranulation 5.0% and with marked degranulation 2.3% respectively. 3) The mid-portion of the small intestine showed the total count to be 15.0±2.54 and of these the normal form was 83.3%, with moderate degranulation 13.3% and with marked degranulation 3.3% respectively. 4) The mid portion of the large intestine showed the total count to be 12.7±2.63 and of these the normal from comprised of 82.6%, with moderate degranulation 11.8% and with marked degranulation 5.5% respectively. 5) When the red pepper was given as a single dose, the total count decreased until 10 hours after administration and showed the least count but later gradually its number increased and returned to normal but reached its maximum beyond the normal control at the 5th day but later returned to normal at the 7th day. 6) The percentage of the decrease in toal mast cell count with a single administration was most marked in the stomach and the nest order is the small intestine, the large intestine, and the esophagus respectively. 7) When the red pepper was given repeatedly the total count decreased continuously as long as the administration continued but gradually the percentage decreased after two weeks period. 8) When the administration reached the 25th time the total count decreased continuously even though the administration was stopped and reached the minimum on at the 3rd day but the number tended to increase after the 5th and reached beyond the normal at the 4th weeks and returned to normal after the 45th day. 9) With the repeated administration the percentage of the total count was most apparent in the small and large intestines and the stomach and the esophagus in that order, the recovery was more quick in the latter group however. 10) Regardless of a single or repeated administration the minimum count in the eophagus and the stomach was similar but the intestines showed more decrease with the repeated administration.