To clarify the role of iron in oxidative stress in skeletal muscle atrophied by immobilization, we investigated the effect of deferoxamine--an iron-chelating agent. Deferoxamine, iron-saturated deferoxamine and double-distilled water (control) were administered subcutaneously from the 4th day after immobilization via osmotic pumps to male Wistar rats (14 weeks old), one ankle joint of which was immobilized in the extended position. After 12 days' immobilization, soleus--typical slow red muscles were collected from both hind limbs and their levels of thiobarbituric acid-reactive substance (TBARS) and glutathione were measured. Deferoxamine suppressed the increase of TBARS and glutathione disulfide in atrophied muscle while iron-saturated deferoxamine did not, which strongly suggests that the iron-chelating action of deferoxamine suppressed the increased oxidative stress. This means that iron plays a very important role in increasing oxidative stress in atrophied muscle. In addition, deferoxamine decreased the degree of atrophy, an effect thought to be mediated by the suppression of oxidative stress.