In rats with ischemic myopathy induced by aortic ligation and 5-hydroxytryptamine, there was good correlation of the skeletal muscle concentration of 99mTc-diphosphonate with the increase of plasma creatine phosphokinase and the decrease in muscle potassium. This radionuclide tracer method can be used to quantitate acute injury in individual muscles and provides a basis for clinical nuclear imaging in patients with a variety of disorders involving muscle fiber damage.