Aneurysm of the subclavian artery is unusual and may have several causes. Cases of atherosclerotic origin have been very uncommon, specially if the aneurysm involves normal subclavian arteries. The authors report a case with these characteristics: a 62-year-old female had noted a tumor in the right supraclavicular fossa for thirty years. Angiographically, it proved to be an aneurysm. She was operated on, and a Dacron tubular prosthesis of 6 mm was implanted. The anatomo-pathologic study of the aneurysm showed typical atherosclerotic changes.