Nitrotyrosine has been widely used as a marker of peroxynitrite formation in normal and diseased tissues. However, studies of normal human aortic intima and atherosclerotic lesions at various stages of development failed to reveal its presence except in a very few specimens of both normal and diseased tissues. The techniques used to detect nitrotyrosine-HPLC with photodiode array detection and Western blotting- were able to identify nitrotyrosine after chemical nitration. Hence peroxynitrite may not be as important in the initiation of atherosclerosis as has commonly been proposed.