Fibromuscular dysplasia is a non-inflammatory disease unrelated to atherosclerosis of the small and medium sized arterial walls, which often affects the renal and carotid arteries and occurs mainly in women. The authors report a case of atypical coarctation of the thoracic aorta due to fibromuscular dysplasia confirmed histologically in a 27 year old man. Arteriography was performed because of hypertension and asymmetry of blood pressure measurements and showed irregular stenosis of the aortic isthmus and of the origin of the left subclavian artery. Surgery comprised resection of the pathological segment of the aorta which was replaced by a prosthetic tube with reimplantation of the left subclavian artery. Histological examination showed fibromuscular dysplasia in perimedial areas and diffusely throughout the media. To the author's knowledge this is the first case to be reported in the medical literature.