SummaryA blood pressure survey was made of a cross-section of tie Belgian population, consisting of about 2.000 people (71% of whom were women) their ages ranging from 20 to 60 years. After ten minutes recumbent rest, four consecutive measurements of blood pressure were made. An interview with each person permitted the existence of Previously known hypertension and possible antihyperensive treatment to be taken into account.The distribution of systolic and diastolic pressures was studied and revealed curves comparable to those in the existing literature. Between the ages of 20 and 40 years, women nave, on the average, lower pressure than men.When the blood pressure (average of 4 measurements) exceeded 140/90 mmHg, another examination was made to three weeks later. On the basis of these two determinations, the individuals were classified as normal (66%)hypertensive (on both determinations more than 160/95 mmHg : 11%) and borderline hypertensive (23%).Among the hypertensives, more than a third were not aware of their condition, a quarter were not treated, and 15 % were hypertensive in spite of treatment.This enquiry, even in its preliminary stage, is very revealing about the frequency of high blood pressure in our country and points out the lack of information of the public as well as of the doctors concerning the pathogenic role of hypertension.