Ambulatory blood pressure monitoring techniques have allowed quantification of blood pressure variations occurring over a 24 hour time. The evaluation of these phenomena has not only allowed us to investigate the mechanisms responsible for cardiovascular regulation, but it has also provided information of clinical value. In particular there is evidence that blood pressure variations are significantly related to cardiovascular complications of hypertension. Progress in technology may allow us to extend these observations by means of non-invasive continuous blood pressure recordings to all those conditions where intra-arterial methods are not allowed.