The incidence of atherosclerotic renal artery stenosis was compared in consecutive renal angiography of 28 hypertensive diabetics and 104 hypertensive non-diabetics. Mean age and sex distribution were comparable. Angiographic evidence of atherosclerotic renal artery stenosis was present in 10 diabetics (36 per cent) and 50 non-diabetics (48 per cent). Stenosis was considered hemodynamically significant if the renal vein renin ratio of the involved to uninvolved side was 1.4:1.0 or more. A renal vein renin ratio equal to or more than 1.4 was observed in 4 of 7 diabetics (57 per cent) and 31 of 47 non-diabetics (67 per cent). Fibromuscular hyperplasia was not seen in diabetics but was present in 12 per cent of the non-diabetics. Hypertension was treated surgically and improved in 2 of 3 diabetics (67 per cent) and in 17 of 19 non-diabetics (89 per cent) with angiographic and hemodynamic evidence of renal artery stenosis. In this series the incidence of atherosclerotic renal artery stenosis of physiologic consequence was not significantly different in hypertensive diabetics when compared to hypertensive non-diabetics.