We aimed to examine hypertension prevalence, awareness, treatment and control in a community sample and investigate the impact of using 24 hour ABPM. Office blood pressure (BP) was taken from the electronic health record. Study BP was measured by standardised methods. Participants were invited to undergo ABPM. Hypertension was defined by accepted thresholds or anti-hypertensive use. Standardised questions assessed awareness and treatment. Control was defined as anti-hypertensive use with BP below normal threshold. There were 931 (45%) participants with office BP, study BP and ABPM. By study BP, hypertension prevalence was 60%, awareness 59%, 60% were treated and 46% controlled. By daytime ABPM threshold, prevalence was 61%, awareness 59%, 59% were treated and 54% controlled. ABPM reclassified 13.5% from normotensive to hypertensive and 14.5% from hypertensive to normotensive. ABPM may not hugely impact population hypertension prevalence but at an individual level it reduces misclassification and facilitates more appropriate management. J Clin Hypertens (Green-wich). 2016;18:697-702. ª 2015 Wiley Periodicals, Inc. Hypertension is a leading risk factor for cardiovascular mortality. In 2009 the World Health Organization estimated that raised blood pressure (BP) caused 51% of stroke deaths and 45% of coronary heart disease deaths worldwide. 1 However, many people with hypertension are undiagnosed 2 and of those who are diagnosed many have poorly controlled BP. 3 Accurate measurement of BP is essential for the diagnosis and management of hypertension. Traditionally , measurements are carried out in a clinical setting and a diagnosis of hypertension is made based on this office reading. Ambulatory BP monitoring (ABPM) provides information over a 24-or 48-hour period and in particular gives important information on night-time BP. Ambulatory BP has been shown to be superior for the prediction of clinical events. 4,5 A systematic review and meta-analysis on the relative effectiveness of clinic BP measurements and home BP monitoring (HBPM) compared with ABPM concluded that treatment decisions based on clinic BP or HBPM alone might result in overdiagnosis of hypertension. 6 A subsequent United Kingdom study on the cost-effectiveness of options for the diagnosis of hypertension in primary care reported that ABPM would reduce misdi-agnosis and save costs. It was suggested that in the United Kingdom the increased costs related to ABPM would be counterbalanced by cost savings from better targeted therapy. 7 The National Institute for Health and Care Excellence (NICE) in 2011 recommended that if office BP is 140/90 mm Hg or higher, ABPM should be offered to confirm the diagnosis of hypertension. 8 The 2013 European Society of Hypertension (ESH) guidelines state that office BP remains the "gold standard" for screening, diagnosis and management of hypertension. 9 They recommend HBPM or ABPM be carried out in certain clinically indicated situations including suspected white-coat hypertension, drug resistance, and hypotensive sympt...