Background: Laryngoscopy and endotracheal intubation may produce adverse hemodynamic effects. Magnesium directly contributes to coronary vasodilatation and inhibits the release of catecholamines, thus attenuating the hemodynamic effects during endotracheal intubation.Methods: In this study, 120 patients candidates for elective surgery were studied in four groups that received 30, 40 and 50 mg/kg magnesium sulfate, and the same volume of normal saline (control). The patient's hemodynamic status at baseline, before laryngoscopy, and 1, 3, 5 and 10 minutes after the laryngoscopy were recorded. ST-segment changes and arrhythmias, and the time and duration of laryngoscopy and extubation were evaluated, too. 4 groups were examined for laryngoscopy effects, tachycardia, bradycardia, hypertension and hypotension.Findings: The mean heart rate in the three groups had no significant changes compared to the control group, but in systolic and diastolic blood pressure and mean arterial pressure the differences were significant. Laryngoscopy effects in the three groups had no significant differences compared to the controls. Laryngoscopy time and extubation time had no significant changes, too. Arrhythmia and ST-segment changes were not observed.Conclusion: The result of the present study shows that the doses lower than 50 mg/kg (30 and 40 mg/kg) of magnesium can be effective in reducing cardiac complications of laryngoscopy and tracheal intubation.