We evaluated the efficacy of isosorbide dinitrate buccal spray (Isomack) in attenuating the cardiovascular response to laryngoscopy and tracheal intubation in 60 patients undergoing elective surgery under general anaesthesia. Patients were allocated to one of three groups of 20 patients each. Group 1 patients were administered placebo buccal spray 90 s before induction of anaesthesia. Groups 2 and 3 had isosorbide dinitrate spray 30 and 90 s before induction of anaesthesia. Systolic, diastolic and mean arterial pressures and heart rate were monitored. After the spray, group 3 patients had a significant decrease in systolic arterial pressure (p less than 0.01). At 1 min after intubation, systolic, diastolic and mean arterial pressures showed a significant increase in group 1 patients (24.9 mmHg, 14.2 mmHg and 18.7 mmHg respectively). In contrast, groups 2 and 3 showed a significant decrease in these parameters (p less than 0.01). Although significant tachycardia was present following intubation in all the three groups, the degree of tachycardia was greater in groups 2 and 3 (p less than 0.01).