Incidences of potentially life-threatening cardiovascular events display a diurnal pattern, tending to be higher in the morning than at other times of day. The recording of blood pressure at pre-defined intervals under everyday circumstances is facilitated by ambulatory blood pressure monitoring (ABPM). This technique shows that systolic and diastolic blood pressures display a circadian rhythm in most individuals. Typically, at the end of the night on arousal, blood pressure surges. This surge coincides with increased cardiovascular events. A recent prospective study conducted in Japan, where the incidence of stroke is high, provides further evidence for the link between cardiovascular events and morning blood pressure surge. Prevalence of both silent ischaemic events and multiple cerebrovascular infarcts was highest among the elderly subjects studied, with the largest increase in blood pressure on awakening. An increased risk of cardiovascular morbidity and mortality is also seen in 'non-dippers' (i.e. individuals in whom the normal nocturnal fall in blood pressure is absent or blunted). ABPM is superior to clinic blood pressure in predicting cardiovascular morbidity and mortality, and this suggests that 24-h blood pressure control may be necessary to gain complete benefit from blood pressure-lowering therapy. Antihypertensive agents with a long duration of action have the potential to provide blood pressure control throughout the dosing interval and thus cover the critical early morning period when the blood pressure surges. Clinical studies that have compared telmisartan with shorter-acting angiotensin II receptor blockers and angiotensin-converting enzyme inhibitors demonstrate that telmisartan has a sustained duration of action, with proven efficacy over the entire 24-h period between doses, including the critical early morning period.