Ambulatory blood pressure monitoring is a more accurate method than office blood pressure measurements and allows a better evaluation of cardio-vascular risk. The indications to perform this test are reviewed here, and the results can considerably help in treatment decision. A good quality recording gives information about the presence or the absence of an arterial hypertension, of white coat and masked hypertension, blood pressure variability and circadian rhythm. However the interpretation and understanding of the results are not always easy. The actual recommended blood pressure values, some technical information and useful tips for ambulatory blood pressure monitoring are reviewed here.