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White coat hypertension (WCH) describes the phenomenon in which blood pressures are elevated in the presence of a health professional measuring the blood pressure—traditionally described (but not exclusively!) in relation to the hospital/clinic doctor, who is usually wearing a white coat. Since the introduction of 24 h ambulatory blood pressure monitoring (ABPM),1 the meaning of WCH has been redefined, and one possible definition of WCH is an abnormal clinic blood pressure but 'normal' ABPM. The latter has also been defined in many ways, but the recent Seventh Joint National Committee (JNC 7)2 suggested that the upper limits of 'normal' ABPM to be 135/85 mmHg while patients are awake and 120/75 mmHg while they are asleep. In contrast, the 1999 World Health Organization/International Society of Hypertension (WHO/ISH) guidelines3 suggest that a 24 h average of home blood pressure of 120/80 mmHg as corresponding to clinic blood pressure of 140/90 mmHg.