The authors examined the blood pressure levels of 5, 358 out-patients of Branch Hospital of Okayama University Hospital, Tottori Prefecture, during the four-year period, from April, 1957 to
March, 1961. The following results were obtained: I. The incidence of hypertension with a systolic blood pressure over 150 mmHg was 20.5% (1,093 cases of 5,358). 2. Patients with hypertension over 40 years of age was 35.9% in male and 41.5% in female. Females showed a higher incidence than males and the incidence rate of hypertension increased with age. 3. There was a tendency in the incidence rate of patients with hypertension decreased in summer and increased in cold seasons.