Oxidative phosphorylation in the rat liver mitochondria was studied as affected thiophosphamide 1, 6 and 24 h 3, 7, 15 and 30 days after administration of the chemopreparation. Considerable changes were found in oxidative phosphorylation. The degree of disturbances is different depending on the period which passed after radiomemetics administration. During the first hours and days oxidative phosphorylation is inhibited more and more, reaching the maximum three days later. In subsequent periods of the studies a gradual restoration of this bioenergetic index is observed. When oxidizing alpha-ketoglutarate by mitochondria the inhibition of respiration and phosphorylation is more profound than in case with succinate oxidation.