It is well known that lidocaine and propranolol possess antiarrhythmic properties. In addition, the former has direct myocardial depressant effects with indirect stimulant effects mediated by the autonomic nervous system and the latter has negative chronotropic, inotropic and dromotropic effects through beta-adrenergic blockade. The heart rate is one of the principle determinants of myocardial oxygen demand, so prevention and treatment of tachycardia are very important during anesthesia. Therfore, the present study was undertaken to evaluate the effects of lidocaine(1mg/kg) and propranolol (0.02mg/kg) on the heart rates and blood pressures in patients with tachycardia(100~120 beats per minute) under halothane-nitrons oxide anesthesia. The results were as follows: 1) In the lidocaine receiving group, the heart rate and blood pressure decreased slightly, but these changes were not statistically significant. 2) in the propranolol receiving group, the heart rate decreased significantly and reached steady value(13bpm, p<0.01) at 7 min and blood pressure decreased slightly, but these changes were not statistically significant. 3) In propranolol-lidocaine mixture receiving group, heart rate decreased significantly and reached to steady value(13bpm, p<0.01) at 5 min and systolic blood pressure decreased about 5 torr(p<0.05), but the diastolic blood pressure remained unchanges. From the above results, it is suggested that the lidocaine and propranolol mixture rather than individual is more valuable in restoring the heart rate and blood pressure to normal value.