Renal arteriography was employed in 51 hypertensive patients in the upright position and was found to have several advantages over conventional techniques. Improved filling of the renal vascular tree was regularly observed and stenotic lesions of the renal arteries were discovered more readily. Nephroptosis was encountered in 12 of 17 patients with fibromuscular hyperplasia of the renal artery. This high incidence suggests that abnormal renal mobility may produce this obscure disease of the arterial wall. Evidence has been found that renal ptosis may cause orthostatic hypertension by elongating and narrowing the renal artery in the presence or absence of underlying stenotic disease.