Clinico-Statistical findings were summarized in 252 cases of clinically diagnosed pericoronitis of the lower third molar. 1) Sex and Age Incidence: Generally speaking it could be seen a little more frequently in male, while more often in female before about 30 years of age, but a contrary tendency could be noticed with the progress of age. Eight per cent of all the cases were between the ages of 20 and 29 years. 2) Seasonal Incidence: It showed a decaease in the order of fall, spring, summer and winter. 3) Side Incidence: Almcst no difference of incidence could be seen between right and left sides. As for inclination of the eruption normal position was most frequent in acute cases, while mesial and horizontal inclincations more frequent in chronic cases. Twenty-eight per cent of all the cases showed the findings of bone resorption of the alveolar process. 4) Clinical Findings: They were almost agreed with those of previous description except lower incidence of disturbed mouth opening and fever which had been considered to be the most frequent symptoms so far. According to the clinical findings all the cases could be classified into acute and chronic ones at the ratio of 15 to 85. As a conclusion the fact that a cusp or a part of the crown had been exposed in all the cases examined may suggest that pericoronitis was due to infection of the dental follicle after eruption and had hardly connection with insufficiency of the space, direction of eruption, and difference of localiztion.