The introduction of IVDSA provides a safer method of angiographic investigation of the aortic arch and brachiocephalic arteries than conventional angiography in patients with cerebro-vascular disease. The quality of visualization however decreases. Instead of changing over to IADSA we find it worthwile to try to improve IVDSA in different ways. One of them is represented in this prospective double blind cross-over study in which we have investigated the effects of using an isotonic non-ionic contrast medium, iohexol (omnipaque), in comparison to meglumin-sodium-diatrizoate (urografin) which is widely used. Iohexol causes less severe side-effects, less severe artifacts and a better image quality. A statistical relation between parameters could not be established. A lag-effect exists for side-effects. The necessity of using low osmolar contrast media is discussed.