The author observed the distribution of mast cells in the hard palate wound healing of healthy male albino rats weighing about 100gm. The mild wounds were made antero-posterior linealy by sugical knife. The results were as follow : 1. At the from three days to five days after wound, the number of mast cells were markedly increased. 2. In the wound healing process, mast cells were more distributed in the lamina propria than in the submucosa.