Renal atrophy due to the renal artery stenosis associated with aortitis syndrome was studied in seven patients. Severe hypertension, high plasma renin activity and normal overall renal functions were present in all. The luminal diameter of the stenosed renal artery seen on the angiogram was less than 1.5 mm at the maximum area of stenosis in all patients. The size of the kidney with renal artery stenosis was diminished, ranging from 8.0 to 14.0 cm in longitudinal diameter on the nephrogram. Histological findings of the small kidney revealed ischemic atrophy. Although the rate of progression of the arterial stenosis was uncertain, the collateral circulation was found to be rich. Renal atrophy was not frequent and not marked even in the presence of high grade renal stenosis or obstruction in case of renovascular hypertension secondary to the arteritis.