The extent to which changes in tissue energy metabolism correspond to the severity of a hemorrhagic shock condition has been studied. In cats, 50% of the blood volume was withdrawn within 10 min, resulting in a fatal outcome within 3 h (range from 45 min to 3 h). Skeletal muscle and blood samples were taken prior to the hemorrhage and in the agonal phase or after 2 h in compensated bled animals. Tissue levels of ATP, CrP, G-6-P, lactate and glucose as well as blood levels of glucose, lactate and pyruvate were determined enzymatically. The results showed no depletion of phosphagen levels in the agonal phase, while glycolytic metabolites, lactate in particular, demonstrated a close correlation to circulatory deterioration and imminent death.