Tracheal intubation is accompanied by varying degrees of sympathetic stimulation as reflected by increases in heart rate and blood pressure. Several clinical trals to reduce these effects on blood pressure and heart rate by employing phar-macologic agents such as alpha-and beta-blockers, calcium channel blockers, narcotics and lidocaine have been reported. To evaluate the effect of clonidine and propranolol on the hemodynamic changes induced by intubation, we administered clonidine (5 ug/kg or 10 ug/kg. p.o.) or propranolol (160 mg, p.o.) 1 hour before induction of anesthesia, and measured heart rate, systolic pressure, diastolic pressure, and mean pressure before induction, after induction and 1, 3, 5, 10, 30 minutes after intubation. The results were as follows. 1) In the control group, intubation caused a significant increase in heart rate (34%) and blood pressure (31%) 1 minute after intubation, but blood pressure returned to normal level within 5 minutes and increases in heart rate continued to 10 minutes after intubation. 2) Increase in heart rate induced by intubation was attenuated by high dose of clonidine (10ug/kg) and propranolol (160 mg), but was not attenuated by low dose of clonidine (5 ug/kg). 3) Pressor effect elicited by intubation was attenuated by high dose of clonidine, but was not affected by low dose of clonidine and propranolol. Above results suggested that oral clonidine one hour before scheduled anesthesia can be a help to reduce to pressor effect and chronotropic effect of intubation.