The incidence of multiple renal arteries was studied by reviewing the translumbar aortograms of 400 patients, 381 of whom had hypertension. Excluding those few with inadequate aortograms, there were 249 hypertensive patients who had normal renal arteries, and 110 who had occlusive disease or aneurysms of the renal artery. Seventy-five% of the patients with renal artery lesions and 75% of patients with normal renal arteries had 1 renal artery to each kidney. The incidence of multiple renal arteries in these hypertensive patients was 25%, no higher than has been recorded generally in anatomic investigations. Eighty-three (31%) of 269 hypertensive patients with a single renal artery on each side and 27 (31%) of 88 hypertensive patients with multiple renal arteries had occlusive lesions or aneurysms.