Functionally significant, nonatherosclerotic, noninflammatory, concentric and tubular stenoses of the abdominal aorta, 4 to 16 cm in length, were encountered in five male and five female patients 11 to 49 years old. Seven patients were younger than 19 years of age. Aortic branch stenoses were common, affecting splanchnic vessels in seven patients and renal arteries in eight patients. The pathogenesis of the aortic constrictive lesions remains unknown, but it may be related to developmental error or aortic growth arrest. Existence of multiple renal arteries in 70% of these patients lends support to the developmental hypothesis. Intimal fibroplasia characterized stenotic aortic tissue. Severe hypertension was common, with the mean preoperative arterial pressure being 200/119 mm Hg. Thoracoabdominal bypass was undertaken in eight patients, being combined with renovascular reconstruction on five occasions. Two patients underwent patch graft aortoplasty with bilateral renal revascularization. Therapeutic results were classified as excellent six times and as good four times. Single-stage arterial reconstructions are the preferred method of treatment for abdominal aortic coarctation or segmental hypoplasia with associated aortic branch disease.