After 48-h ambulatory blood pressure monitoring, the incidence of ischaemic stroke, nephropathy, coronary heart disease and retinopathy was prospectively assessed for 6 years in 297 subjects, including 176 treated patients with an elevated blood pressure mean (MESOR-hypertensives). The relative risk associated with an excessive circadian blood pressure amplitude is 8.2 (95% confidence interval 3.1 to 21.7; p < 0.001) for ischaemic stroke and 6.9 (2.9 to 16.3; p < 0.001) for nephropathy. In MESOR-hypertensives, the relative risk for ischaemic stroke and nephropathy is 6.3 (p < 0.005) and 4.0 (p < 0.05), respectively. In MESOR-normotensives as well, an excessive circadian blood pressure amplitude is associated with a large increase in risk for ischaemic stroke and nephropathy (p < 0.05). An excessive circadian blood pressure amplitude is an entity in its own right that increases the risk of adverse vascular events irrespective of the blood pressure MESOR, age and the presence of other known risk factors. The diagnosis of this condition requires around-the-clock monitoring of blood pressure. The treatment of patients with this condition should aim not only at lowering the blood pressure mean but also at reducing blood pressure variability within 24 h.