Summary: Secondary forms of hypertension account for only a small fraction of the overall hypertension prevalence, which is largely due to primary hypertension. However, their true prevalence is not precisely known,because available data may be confounded by the selection bias of the studies reported in the literature, the number of undiagnosed cases and the varying definition of secondary forms of hypertension. Nevertheless, despite their limited prevalence, detection and management of secondary forms of hypertension is of utmost importance, because these forms often carry a high or very-high risk of morbidity and mortality and can possibly be cured by timely treatment of their cause . Secondary forms of hypertension require specific diagnostic approaches, which allow to detect their specific causes and to select effective drug treatment or appropriate interventional treatment that control or cure the elevated BP. Secondary forms of hypertension are a frequent cause of severe or true resistant hypertension, worsening of previously controlled hypertension or increased severity of target organ damage, which may appear as disproportionate to the duration of hypertension. Although secondary forms of hypertension are particularly frequent in younger patients (below 40 years) with an elevated BP, some forms (such as atherosclerotic renovascular disease) are more common at an older age. Screening all hypertensive patients for secondary hypertension is not feasible or cost-effective. However, secondary forms of hypertension frequently show clinical findings that suggest their presence and even their specific nature.