Objective: To evaluate the effect of irradiation on adenosine triphosphate (ATP) catabolism in skeletal muscles. Methods: Thirty-six inbred female mice were used in the study. The animals were randomly divided into five irradiated groups and one unirradiated group as control. The left hind legs of the mice in irradiated groups were exposed to a single-dose γ-irradiation of 60 Gy. The concentrations of adenosine monophosphate (AMP), adenosine diphosphate (ADP) and ATP in the irradiated gastrocnemius muscles were determined by high-performance liquid chromatography. Results: In the early periods after irradiation, a significant reduction of the three examined substances was observed in the irradiated gastrocnemius muscle compared with the controls (P 0.05), whereas the concentrations of AMP, ADP, and ATP in the irradiated legs recovered to the normal level 30 days after irradiation. Conclusion: ATP catabolism in skeletal muscle was influenced by radiation in the early stage. This early disorder of ATP catabolism in the irradiated skeletal muscle might be one of the potential factors that initiate the morphological and functional changes of the muscle in late periods after irradiation. Keywords: γ-irradiation, trismus, ATP catabolism, skeletal muscle, HPLC