We investigated the effect of urinastatin on energy metabolism disorder during shock. Intravenous administration of urinastatin at the dose of 50,000 U/kg ameliorated the decrease in total adenine nucleotide (TA) levels and in energy charge (EC) of liver and pancreas during traumatic-shock induced by the Noble-Collip drum method in rats. Urinastatin, at a concentration of 3,000 U/ml, suppressed the decrease in EC of rat liver slices exposed to the medium including 10% serum obtained from traumatic-shock rats. Aprotinin showed a similar effect. Depression in respiratory activity of liver mitochondria exposed to the shock rat serum was also ameliorated by 1,000 U/ml of urinastatin, but aprotinin failed to reverse this depression. In the isolated rat livers perfused with normal rat serum, urinastatin at the concentration of 3,000 U/ml did not affect ATP and TA levels and EC. These results suggest that, unlike aprotinin, urinastatin ameliorates the depression of energy metabolism in liver during shock without affecting normal energy metabolism, probably by antagonizing the actions of depressant factors released into blood during the shock state and by protecting against the decrease in the adenine nucleotide pool.