The arterial baroreflex buffers abrupt transients of blood pressure and prevents pressure from rising or falling excessively. In experimental animals, baroreceptor denervation results in temporary or permanent increases in blood pressure level and variability, depending on the extent of denervation. In humans, the clinical syndrome of baroreflex failure may arise from denervation of carotid baroreceptors following carotid body tumour resection, carotid artery surgery, neck irradiation and neck trauma. The syndrome is characterised by acute malignant hypertension and tachycardia followed by labile hypertension and hypotension. Baroreflex failure can be a cause of secondary hypertension and should also be considered in the differential diagnosis of pheochromocytoma. Patients with suspected baroreflex failure should be referred to specialised centres for diagnostic testing and treatment.