It has long been recognized that naturally occurring substances in higher plants have antioxidant activity. Recently, there is a growing interest in oxygen-containing free radicals in biological systems and their implied roles as causative agents in the aetiology of a variety of chronic dis-orders. Accordingly, attention is focused on the protective biochemical functions of naturally occurring antioxidants in the cells of the organisms containing them. Antioxidants in the oils are important in the stabilization of free fatty acids. The antioxidant activity of phenols and other compounds present in oils has been well and widely studied by several authors. Besides, reports concerning the local uses, pharmacological features of the extracts and the essential oils of several Achillea species have been cited in the literature.