A 29 year old white man presented to general practice after a routine check at work, which was carried out because he felt lightheaded. His work found a blood pressure of 178/104 mm Hg and a pulse rate of 100 beats/min. His cousin, who was a nurse, rechecked his blood pressure and found it to be 138/92 mm Hg. He was not a regular attendee at the surgery and was taking no drugs. He had occasionally felt lightheaded during the past year, but he had never fainted. He had a family history of high blood pressure. He was slim (body mass index of 20), and in the surgery he had a blood pressure of 172/94 mm Hg and a pulse rate of 98 beats/min. Optic fundi, peripheral pulses, heart sounds, and chest examination were all normal. He had no abdominal bruits.