Objective: Data from referral centers suggest that approximately 10% of hypertensive patients could have secondary hypertension (2HTN). It is commonly accepted that 2HTN is more frequent in younger subjects but its prevalence is not known. Design and method: Retrospective analysis of the computerized medical records of consecutive hypertensive patients aged 18 to 40 years referred to the Georges Pompidou ESH hypertension center who underwent in-hospital work-up including renal artery duplex ultrasound or CT angiography, determination of plasma aldosterone/renin ratio and 24 h urinary metanephrine. Results: Between January 2008 and December 2013, 843 patients (52.2% women) aged 26.9 ± 6.2 years were referred to our center. 509 patients (60.4%) had a family history of hypertension and 356 (42.4%) had a body mass index exceeding 27 kg/m2. BP levels were 142.0/89.2 mmHg with a median number of 1 (range 0–7) antihypertensive drugs. 250 patients (29.6%) were diagnosed with 2HTN including primary aldosteronism in 62 patients (7.4 %), fibromuscular dysplasia in 49(5.8%) and pheochromocytoma in 33 (3.9%) patients. Conclusions: Before the age of 40, the prevalence of 2HTN is close to 30%. This high prevalence confirms the necessity of a systematic work-up for 2HTN in younger adults. Further analysis will aim to identify the phenotype based on the cause of hypertension.