To determine the efficacy of nalbuphine in preventing the increase in heart rate and mean arterial pressure in response to laryngoscopy and orotracheal intubation.A comparative trial.Department of Anaesthesia, Pakistan Naval Hospital Shifa, Karachi, Pakistan, from January 2001 to January 2002.Forty healthy patients having general anaesthesia for elective surgery, were selected by convenient sampling to receive either saline [group I (control group); n= 20] or nalbuphine 0.2 mg/kg; (group II; n = 20) as a bolus dose, 5 minutes before laryngoscopy. Double blinding was done as the patient as well as the researcher was not aware of which study drug was being given. Heart rate (HR) and mean arterial pressure (MAP) were measured before induction of anaesthesia (time 1), just after intubation (time 2), then after every minute upto 5 minutes (time 3-7) and after 10 minutes of intubation (time 8). Twenty percent rise in heart rate (HR) and mean arterial pressure (MAP) was considered as significant. Data were analyzed by using SPSS version 10. Student's t-test was used for the significance of parameters at p < 0.05 and analysis of variance test (ANOVA) was interpreted for group analysis of the parameters.There was a significant increase (p <0.05) in heart rate (53.4%) in group I after intubation at time 2 compared with baseline at time 1, as compared to group II (15.5%). The HR gradually decreased during time 3 to 8 but still remained slightly higher than group II. MAP also increased significantly (p <0.05) in group I, at time 2 (43.6%) compared with baseline at time 1 as compared to group II (10.5%). The MAP also gradually decreased during time 3 to 8 but remained on slightly higher level than group II.Nalbuphine 0.2 mg/kg prevented a marked rise in heart rate and mean arterial pressure associated with laryngoscopy and orotracheal intubation.