The method of measuring cardiac-pump function with electromagneticflowmeter was studied in rats. CI, SVI, AFV and dF/dt measured in 20 nor-mal rats were 227 + 7 ml/kg/min, 0. 50 ? 0. 0.2ml/kg, 3. 35 ? 0. 17ml/secand 167 ? 9 ml/sec~2, respectively. The physiological status of the modelwithin 60 minutes was stable, When volume loading was given, CI and SVI of normal rats were incr-eased by 183 ? 8% and 190 ? 9%, AFV and dF/dt also increased significantlywith less degree (83 ? 8% and 64 ? 5%). The comparision of the pump function indices of the normal and themyocardial infarcted rats showed that during volume loading, the changesof pump function and its response curve were helpful to assess the damageof cardiac function.