This observation was carried out to investigate the phosphatase activity and the calcium contents of periapical granuloma in patients of both sex and different age. The results were as follows : 1. Acid phosphatase activity was considerably increased with bone absorption. 2. Alkaline phosphatase activity was also remarkably increased in periapical granuloma. 3. In case of periapical granuloma, differences of phosphatase activity by age and sex were not observed. 4. Calcium contents in periapical granuloma was of very small quantity, showing remarkable decrease when compared with the normal bone tissue.