A survey of the ECG findings (Minnesota Code) in 1906 cases was performed in Okayama Prefecture since 1966 with follow-up till 1976. 1) The blood pressure, especially diastolic blood pressure, was well controlled with adequate antihypertensive therapy. 2) It was rare to alter to other ECG codes in those who had initially shown code 3 combined with code 4 and/or code 5. 3) During the period studied, there were little or no changes in ECG code of individuals showing code 4 in the initial study. 4) Code 5 was found more frequently in female, and restoration of the code to normal ECG (code 1-0) occurred in a considerable population during the follow-up. 5) Out of 918 subjects, 307 male and 611 female, the mean values of blood pressure during the second half (1971-1976) was lower in majority of subjects with a moderate or severe hypertension compared to those in the first half (1966-1970). 6) Along with an elevation in blood pressure, code 1-0 in ECG decreased and the codes for left ventricular hypertrophy increased. 7) Among the 741 cases who had ECG code 1-0 in 1966, the prevalence rate of the code was 77.1% in 1970 and only 57.2% in 1976. 8) Out of those starting out in ECG code 1-0 in 1966 and showing normal blood pressure, urinalysis and physical examination during the survey, 84.9% remained in ECG code 1-0 in 1976.