BACKGROUND: A laryngoscopy and endotracheal intubation cause an increase in the blood pressure and heart rate. Remifentanil is an opioid that is often used to reduce the hemodynamic responses after tracheal intubation. This study evaluated the effect of three bolus doses of remifentanil on the hemodynamic responses to a laryngoscopy and tracheal intubation. METHODS: Eighty patients, aged 35-65 years, with an ASA physical status of I and II were randomly divided into four groups containing 20 patients each. Anesthesia was induced with propofol 2 mg/kg followed 30 s later by saline (control) or remifentanil 0.5 (R0.5), 1 (R1) or 2 (R2)µgram/kg given as a bolus over a 30 s period. A laryngoscopy and tracheal intubation were performed 90 s later (corresponding to 3 min after induction), and anesthesia was maintained using 2% sevoflurane and 50% nitrous oxide in oxygen. Rocuronium 1 mg/kg was given as a neuromuscular block. The systolic arterial blood pressure (SAP) and heart rate (HR) were recorded until 5 min after intubation. ESULTS: In all groups, the SAP decreased after inducing anesthesia and then increased after intubation in all groups (P < 0.05), but the maximum increases (46, 15, and 9 mmHg in the R0.5, R1, and R2 groups, respectively) after intubation were lower in the remifentanil groups than that of the control group (73 mmHg) (P < 0.05). The HR decreased in the remifentanil groups while it remained stable in the controls after the induction of anesthesia. However, it increased after intubation in all groups. The mean maximum HR (83, 71, and 69 bpm in the R0.5, R1 and R2 groups, respectively) was significantly lower in the remifentanil groups than that in the controls (98 bpm) (P < 0.05). All remifentanil doses significantly attenuated the pressor and tachycardiac responses (P < 0.05). CONCLUSIONS: All remifentanil doses were effective in controlling the pressor and tachycardiac response to endotracheal intubation in patients in whom anesthesia was induced with propofol. However, the use of the 1 and 2µgram/kg dose was associated with a decrease in the SAP to less than 85 mm Hg in 10 patients (50%) each. Therefore, 0.5µgram/kg appears to be the optimal dose to attenuate the cardiovascular responses to endotracheal intubation in patients.