Summary: To compare the cardiotoxicity induced by ropivacaine and bupivacaine and to investigatethe mechanism of cardiotoxicity, 24 mature New Zealand rabbits were divided randomly into controlgroup (group C), ropivacaine group (group R) and bupivacaine group (group B). Hearts were drawnout rapidly from the anesthetized animals and cardiac perfusion was performed immediately. Ropiva-caine 500 ng/ml (group R) or bupivacaine 500 ng/ml (group B) was added to the perfusion solution.Ventricular myocardial ATP, ADP and AMP were measured with high performance liquid chro-matogram. The ability of myocardial mitochondria oxidation to pyruvate or palmitoylcarnitine wasdetected with Clark electrode. Our results showed that myocardial ATP and ADP decreased signifi-cantly (P＜0. 05) in group R and most significantly (P＜0. 01) in group B as compared with groupC. Myocardial ATP and ADP decreased most significantly (P＜0. 01) in group B as compared withgroup R. The changes of myocardial AMP revealed significant difference among three groups. Thechanges of pyruvate oxidation exibited no significant difference among the three groups. Palmitoyl-carnitine oxidation decreased markedly (P＜0. 05) in group R and most significantly (P＜0. 01) ingroup B as compared with group C. The present study indicated that the inhibition of lipid substrateoxidation may be responsible for the cardiotoxicity induced by bupivacaine and ropivacaine. The car-diotoxicity induced by ropivacaine is far more less than bupivacaine.