RENAL artery aneurysms, once considered rare, are being recognized with increasing frequency. Garritano, 1 in 1957, collected 175 cases dating back to 1770. 2 In the decade since 1957, approximately 170 additional cases of renal artery aneurysm have been reported, bringing the total to 345. With the expanded use of aortography and selective renal angiography in the evaluation of patients with vascular disease and suspected renovascular hypertension, the number of cases will undoubtedly continue to increase. Aneurysms of the renal artery are said to constitute 1% of all aneurysms. 3 Based on autopsy studies the incidence in the general population ranges from 1 in 7,000 4 to 1 in 11,000. 2 A study of hypertensive patients reveals a considerably higher incidence of 1 in 112. 5 Schwartz and White 6 reported an incidence of 15 in 154 based on renal arteriograms made in unselected autopsy specimens. Renal artery aneurysms are