We studied the cell composition and free radical oxidation in the bone marrow of white outbred rats after hypokinetic stress (24 and 72 h) and the effects of exogenous glucocorticoid triamcinolone acetonide (2 mg/kg; injected 24 h after hypokinesia); the measurements were performed in 96 h after drug administration. The hypoplastic effect of the glucocorticoid after 24-h hypokinesia was observed against the background of reduced free radical oxidation. In animals subjected to 3-day hypokinesia, the resistance of the bone marrow to the hypoplastic effect of this drug was accompanied by activation of free radical processes.