Blood pressure has been measured in a cohort of 2300 high school students of Milan (14-15 years old) for two years on end. The prevalence of "borderline hypertension" was 11.5% at the first examination and 8.5% at the second. The values of blood pressure were decreased, in every measurement, after a year from the initial screening especially in "borderline hypertensives". This study has confirmed that the "borderline hypertension" in subjects 14-15 aged is a transient phenomenon, but the incidence of "stable hypertension" as been found higher significantly in "borderline hypertensives" than normotensives. The results are discussed.