EXTENSIVE AND COSTLY INVESTIGATIONS: Are not warranted in the vast majority of hypertensive patients. Characteristics identifying the patients at risk for secondary hypertension can be used to define the small percentage of patients with hypertension who require more extensive diagnostic testing and management of their condition. Exposure to certain medicines, foods or drugs may cause reversible rises in blood pressure. Renovascular and adrenal diseases cause curable forms of hypertension. IN MANY CASES, THE PATIENT'S HISTORY: Examination and simple tests can detect such exposures and disorders. Checking for secondary hypertension is therefore an early step required for the management of all patients with hypertension, provided it is based on clinical signs and inexpensive tests. This primary screening cannot exclude the possibility of renovascular or adrenal disease in a small number of asymptomatic patients. The risk of missing a diagnosis is acceptable provided that blood pressure is normalized by non-specific antihypertensive treatment. However, more extensive etiologic investigation is required in patients who subsequently develop resistant hypertension. This secondary screening requires imaging and biochemical tests that are not required for primary screening. CORRECTION OF THE CAUSES: Of secondary forms of hypertension may restore blood pressure to normal. The patient's age affects the reversibility of renovascular and adrenal hypertension after etiologic treatment: the younger the patient, the higher the probability of blood pressure normalization.