A randomized study was carried out to determine whether postoperative administration of either intranasal nifedipine or intravenous diltiazem was effective in preventing hypertensive episodes after carotid endarterectomy. Sixty-three consecutive patients undergoing this surgery were randomly assigned to three groups (n = 21): control (C), nifedipine (N) and diltiazem (D). Anaesthesia was induced with flunitrazepam (0.02 mg X kg-1), fentanyl 6 micrograms X kg-1 and pancuronium (0.1 mg X kg-1), and maintained by N2O/O2 (50%), additional fentanyl and halothane or enflurane when warranted. Postoperatively, patients were warned whilst under mechanical ventilation in a recovery room. Upon arrival in the recovery room, intranasal nifedipine (10 mg) was given to patients included in group N, while patients from group D received an intravenous dose of 0.3 mg X kg-1 of diltiazem, followed by a continuous infusion of 3 micrograms X kg-1 X min-1 until 15 min after extubation. No preventive treatment was given to patients in group C. If postoperative systolic blood pressure rose to more than 180 mmHg, 10 mg of nifedipine were administered intranasally. During the postoperative period, 13 patients from group C, 5 from group N and 4 from group D exhibited hypertensive episodes (systolic blood pressure greater than 180 mmHg or diastolic blood pressure greater than 100 mmHg). Intranasal administration of 10 mg nifedipine led to the normalization of blood pressure in 20 out of these 22 patients. This study confirmed the high incidence of hypertensive attacks after carotid endarterectomy, and showed that prophylactic administration of nifedipine or intravenous diltiazem was highly effective in preventing such hypertensive episodes.