Eighty-three patients out of 8,525 undergoing renal angiography during the years 1970-1979 were found to have renal artery aneurysm, which in six patients were bilateral and in 11 multiple. This corresponds to an incidence of almost 1% in this group of patients. Sixty-nine patients were treated conservatively and followed for a mean of 4.3 years. At that time nine patients had died. The cause of death was in no case related to the aneurysm. None of the 60 living patients had symptoms which could be related to the aneurysm. Reports of 36,656 autopsies, including most of the sudden deaths occurring in southern Sweden during a ten-year period, were analyzed. Nineteen cases of ruptured arterial aneurysms in the branches of abdominal aorta were found, but in no case were the renal arteries involved. It is concluded that the risk for rupture of a renal artery aneurysm is extremely small. The indications to operate renal artery aneurysms are discussed.