Transient increases in blood pressure and heart rate following laryngoscopy and endotracheal intubation are well documented in normotensive patients. These circulatory effects are alicited by mechanical stimulation of the laryngopharynx and traches via efferent cervical sympathetic fibers. The hypertension during induction of anesthesia in hypertensive patients can be sccompanized by cerebreal hemorrhage, left ventricular failure and life breatening cardiac arrhythmia. The present study was undertaken to observe the effects of sodium nitroprusside(SNP) on the change in systolic blood pressure and heart rate during and after laryngoscopy for tracheal intubation. Eight adult patients who had received elective operation under general anesthesia with endotracheal intubation were randomly selected and devided into 3 groups. Group l served as a normotensive group. Group ll served as a hypertensive group withou SNP. Group lll served as a hypertensive group receiving 1ug/kg of SNP 15 seconds before starting laryngoscopy. The changes of systolic blood pressure and pulse rate were analysed and data were compared between groups. The results were as follows: 1) Attenuation of increase in blood pressure was statistically significant in the hypertensive group with prior SNP compared with the group not receiving SNP (p<0.05). The magnitude of blood pressure increase in the hypertensive group without prior SNP was significantly greater than in the normotensive group(p<0.001). 2) SNP had no effect on the increase in heart rate associated with tracheal intubation. In conclusion, it is suggested that a single rapid intravenous injection of SNP is a practial pharmacological method to attenuate blood pressure increase during direct laryngoscopy and tracheal intubation in hypertensive patients.