Psoriasis is a chronic inflammatory immune-mediated skin disease that causes red dry patches of thickened skin with reactive abnormal epidermal differentiation in which genetic and environmental factors have a significant role. Therapeutic agents either modulate the immune system or normalize the differentiation program of psoriatic. Etanercept (ETN) is a new, safe and effective treatment for moderate to severe psoriasis. This study aimed to investigate the situation of thiol/disulfide homeostasis in saliva and serum of Iraqi psoriatic patients compared to that of healthy individuals, as well as study the impact of its treatment with Etanercept on this homeostasis in saliva and serum of these patients.