Endotracheal intubation following anesthesia induction frequently produces hypertension and tachycardia. This study evaluated the efficacy of preinduction IV labetalol for attenuating the hemodynamic responses to intubation following thiopental and succinylcholine induction of anesthesia. Two hours after diazepam (10 mg by mouth), 60 patients were randomized in a double-blind manner and received IV saline or labetalol at doses of 0.25, 0.5, 0.75, or 1 mg/kg in a parallel design study. Five minutes later, thiopental (4 mg/kg) and succinylcholine (1 mg/kg) were administered, and the trachea was intubated in 2 minutes. Nitrous oxide (70%) anesthesia was maintained for 10 minutes. Hemodynamic parameters were grouped and analyzed for significance (p less than 0.05) by two-way repeated measures analysis of variance and t-test with Bonferroni adjustments. Baseline group demographics and hemodynamics were comparable. All doses of labetalol significantly attenuated the rate-pressure product increase immediately postintubation versus placebo. There was a dose-dependent attenuation of the increases in heart rate and the systolic, diastolic, and mean blood pressures versus placebo following intubation. IV labetalol at doses up to 0.75 mg/kg offers an effective pharmacologic means of attenuating preoperative hemodynamic responses to endotracheal intubation.