The statistic observations were made about the inpatients and out-patients of the department of oral surgery, okayama university medical school during full five years from July in 1950 to June in 1955. The out-patients were classified into those of inflammation (pulpitis and gingivitis excepted), of caries (which was divided into what needed canal treatment and what was not so serious), of pyorrhea alveolaris, of gingivitis, of tumour, and of other diseases, and then each disease group was observed according to the difference year, season, tooth, sex, age, and occupation. Thereby, comparatively remarkable, interesting, statistical, numeral values were not only obtained concerning to each disease, but also the characteristics of the department of oral surgery of the attached hospitals of our government universities were apparently recognized here also. As the total number of the in-patients was only 237, the detailed statistical report being reserved, they were observed only according to the difference of year and disease. Thereby, inflammation and tumour were so many that they occupied about 80% of the number of all the in-patients.