Amifostine is one of the cytoprotective drugs used during anticancer therapy. Amifostine as a thiol compound possesses antioxidant properties and protects only healthy cells against damage, mainly by scavenging reactivity oxygen species, competing with oxygen to prevent oxygen radical interactions with DNA, and promoting cell repair through hydrogen donation to reactive oxygen species. The aim of the present study was to evaluate antioxidative ability of amifostine in blood serum of rats exposed to cyclophosphamide during two weeks after drug administration. We show that amifostine only to a small degree prevents disorganisation of antioxidant systems of blood serum of rats caused by cyclophosphamide action. It is probably connected with low concentrations of amifostine active metabolites in the serum.