The development and clinical application of ambulatory blood pressure monitoring (AbpM) has brought several of the main features of the circadian blood pressure (bp) rhythm to light. AbpM has shown to be a very useful method in cardiovascular risk assessment and remains the only method of diagnosing a non-dipping blood pressure profile. A ‘non-dipping’bp profile is currently regarded as a risk factor in its own right for cardiovascular (Cv) events and target organ damage. Nevertheless, the reliability of AbpM in assessing dipping status is still being questioned. furthermore, a clear-cut definition of ‘non-dipping’has not been established so far. The pathophysiological mechanism (s) of a non-dipping profile might involve abnormalities in extracellular volume and/or vascular resistance regulation. in addition, differences in daytime and nighttime activity, sleep quality and body position during sleep are involved as well. A reduction in cardiovascular risk by a pharmacologically induced switch from a non-dipper to a dipper status might be expected, but remains to be proven.