Blood pressure (BP) varies according to cycles characterized by a reduction during sleep and an increase on awakening. The nighttime decrease is absent or blunted in some patients (termed "non-dippers"). Cross-sectional and prospective data have shown that non-dippers have more target organ damage than have dippers in normotensive and hypertensive subjects. We reviewed the English language literature regarding this association. A non-fortuitous association seems to exist between non-dipper status and cardiovascular risk such as stroke and cardiac events. Among diabetic patients, this phenomenon has been described to occur more often in individuals with autonomic neuropathy and with different degrees of diabetic nephropathy. In normoalbuminuric normotensive type I diabetic patients without any degree of autonomic dysfunction, according to traditional cardiovascular tests, diastolic BP (dBP) night/day ratio is associated with an increased glomerular filtration rate and an increased extracellular volume. The disruption of the circadian rhythm of sympathovagal activity in non-dipper patients was associated with higher levels in systolic BP (sBP) and dBP and with a reduced decline in sBP and dBP levels during the night. Therefore, the prognostic implications of the non-dipper status may be important since the overall 24-h blood pressure load is elevated in these individuals. These data suggest that patients in whom blood pressure decreases during the night incur less damage to their brain, kidneys, heart, and blood vessels than people with elevated nocturnal BP.