Both ketamine and tracheal intubation are associated with increased heart rate (HR) and systolic blood pressure (SBP). Beta blockers prevent or attenuate this increase. Esmolol (E) is a new, intravenous, rapidly metabolized beta blocker. An open-label study was performed in 41 ASA Class II and III patients divided into groups 1–4: control, 100, 200, and 300 µg·kg−1· min−1(n = 10, 10, 11, and 10, respectively). E was infused over 10 min, the first onefourth of which was a loading dose of 500 µg · kg−1· min−1; at 4 min, ketamine was followed by succinylcholine, intubation, and enflurane–N2O–O2. HR, SBP, blood E, and plasma catecholamine levels were obtained during the 40 min of study. The control group had a baseline HR of 83 ± 5 beats/min while esmolol groups 2–4 had an HR of 73 ± 3, 72 ± 3, and 68 ± 4 beats/min, respectively (P< 0.05). After ketamine, the control group HR increased to 93 ± 6 beats/ min and groups 2–4 remained at the baseline level, 73 ± 3, 73 ± 3 and 67 ± 4 beats/min, respectively (P< 0.05). Postintubation, the control increased further to 113 ± 5 beats/min while groups 2–4 were significantly less, 91 ± 5, 84 ± 3, and 78 ± 4 beats/min, respectively. The mean SBP in most E groups was less than the control within groups, but only in group 4 between groups was the SBP less at postintubation (P< 0.05). Catecholamine levels were the same in all groups and were increased at postintubation. Blood E levels were dose-related and at minutes 4 and 9 the higher levels corresponded to lower HR; there was no active drug or clinical effect at 10 and 30 min postinfusion. No adverse effects of the drug were seen. E, therefore, prevents the tachycardia and attenuates the hypertension associated with ketamine and subsequent tracheal intubation.