The term ‘masked hypertension phenomenon’ was first described by the late Professor Thomas Pickering and is commonly defined as having a normal clinic blood pressure (BP) but an elevated ‘out of office’ reading. In the main, these elevated readings have been provided through ambulatory BP monitoring (ABPM), but sometimes home BP monitoring is used. It is now largely accepted that ABPM gives a better classification of risk than clinic BP. Thus, the elevated ABPM levels should relate to higher cardiovascular risk, and it follows that these people may be regarded as being genuinely hypertensive and at higher cardiovascular risk. The problem for clinical practice is how to identify and manage these individuals. The phenomenon should be suspected in individuals who have had an elevated clinic BP at some time, in young individuals with normal or normal–high clinic BP who have early left ventricular hypertrophy, in individuals with a family history of hypertension in both parents, patients with multiple risks for cardiovascular disease and perhaps diabetic patients. Masked hypertension appears to be more prevalent in individuals of male gender, with younger age, higher heart rate, obesity or high cholesterol levels and in smokers. Those with masked hypertension are at higher risk of events such as stroke and have a higher prevalence of target organ damage, for example, nephropathy. In conclusion, most of the debate around this topic relates to its reliable identification. Given the higher ambulatory mean blood pressure values there is an increased cardiovascular risk making this diagnosis important.