Secondary hypertension is a condition with high blood pressure with an identifiable cause. Of the total number of patients with hypertension, between 5 and 10% of patients have secondary hypertension. Etiologically, causes for the elevation of the blood pressure can be divided into renal, endocrine, vascular and other. The mechanisms responsible for the blood-pressure growth are various, most often due to these disorders: increased sympathetic activity with consequent vasoconstriction, increased levels of angiotensin and aldosterone with salt retention, and vasoconstriction, and impeded vascular reactivity with reduced production of NO and increased endothelin activity. Diagnostics of secondary hypertension start with a well-taken patient's history and thorough physical exam that can either exclude or draw attention to certain causes. Further diagnostic procedures consist of laboratory and imaging methods that can confirm our suspected diagnosis. Besides that, for Obstructive sleep apnea, a specific cause of secondary hypertension, polysomnography is a vital diagnostic tool. Treatment-wise, it is important to identify and treat eventual hypertensive episodes that can have serious consequences on a patient's health. The regular modality of treatment is antihypertensive therapy with the specific treatment for the basal cause of the disease. Specific prevention of secondary hypertension does not exist. Nevertheless, reducing body weight, proper diet, no alcohol or cigarette consumption, and physical activity benefit the reduction of blood pressure, and should be recommended to all of the patients.