BACKGROUND: Exogenously administered epinephrine under enflurane anesthesia was known to have mild myocardial sensitizing effect. And N2O activates the sympathetic nervous system mildly. We planed this study to confirm cadiovascular effects of clinically administered epinephrine for hemostasis under the enflurane-N2O anesthesia during tonsillectomy. METHODS: Eighty children scheduled to have tonsillectomy were selected randomly and divided into 2 groups as follows; Group E: 1:100,000 epinephrine 2ug/kg and Group EL: 1:100,000 epinephrine containing 1% lidocaine 2 g/kg. Blood pressure, heart rate, and the occurrence of arrhythmia were evaluated before injection, at injection, 1 min, 2 min, 3 min, 5 min and 10 min after injection and 1 min after operation start. RESULTS: In both groups, systolic and diastolic blood pressure and heart rate are increased. But there are no significant statistical differences in each group and between groups. One min after operation, there are significant increases in systolic and diastolic blood pressure and heart rate in both groups (p<0.05), but there is no significant difference between groups. CONCLUSION: Under the enflurane-N2O anesthesia of children, 1:100,000 epinephrine 2ug/kg used for hemostasis could be used comparatively safe without any significant hemodynamic changes. But because there is always the possibility of myocardial sensitization, careful observation is necessary during epinephrine injection under the enflurane-N2O anesthesia.