A defect in fibrillin integrity predisposes patients with Marfan syndrome to vascular wall abnormalities, most notably aortic rupture and dissection. Renal vascular anomalies have not been described previously in children with Marfan syndrome. In this report, we detail data from a hypertensive 14-year-old girl with clinical stigmata of Marfan syndrome and a diagnostic evaluation significant for characteristic aortic root dilatation and aneurysm, as well as a disparity in renal size and function exacerbated by captopril administration. Renal arteriography confirmed a left main renal artery stenosis that was not amendable to balloon angioplasty. Surgical resection resulted in significant improvement in hypertension. Pathological examination of the resected renal artery segment revealed intimal proliferation, fragmentation of the elastic media, and inner medial dissection. This patient demonstrates that, in addition to the aorta, renal arteries can be affected with the characteristic vascular wall pathology of Marfan syndrome, resulting in systemic hypertension. These data suggest that children with Marfan syndrome and hypertension need to be evaluated carefully for the presence of renal anomalies.