There are few data on the prevalence of hypertension in European populations based on the ambulatory determination of blood pressure. The Prognostic Indicator of Cardiovascular and Cerebrovascular Events (PROOF) study provided an opportunity to examine this prevalence in a cohort of 955 patients (387 men and 588 women, all aged 65 years) selected from an electoral list. All patients benefited from measurement of blood pressure during consultation and by 24-hour ambulatory determinations. In this population, 18% had treated hypertension, but 31% had a daytime systolic pressure >135 mm Hg. This proportion was even higher (46%) in patients whose fasting blood glucose was >1.1 g/L or >6.1 mmol/L. In the untreated population, 21% had unrecognized hypertension with daytime systolic pressure >135 mm Hg, with an even higher percentage (35%) in the hyperglycemic patients. This study shows a significant proportion of hypertensive patients, whether treated or not, with high ambulatory blood pressure, especially in those with hyperglycemia who have a higher risk of complications.