Hemorrhage is the most frequent complication of tonsillectomy and is responsible for the majority of post-tonsillectomy fatalities. The incidence of this hemorrhage has been reported to be as high as 20% . Despite continued efforts to reduce this problem, it remains a persistent risk. The charts of 1138 patients who underwent tonsillectomy with or without adenoidectomy from 7-1-89 to 6-30-93 were reviewed. Post-tonsillectomy hemorrhage occurred in 36 patients (3%). Preoperative, intraoperative and postoperative risk factors were assessed. Postoperative bleeding occurred more often in older patients (69% over age 11 years). Seventy-five per cent of these patients were operated on for chronic tonsillitis as compared to 11% operated on for upper airway obstruction. The majority of these patients presented after postoperative day 1 (83%). Four patients required blood transfusions. Postoperative hemorrhage occurred in 14% of patients with elevated postoperative mean arterial pressures. Intraoperative blood loss that exceeded 50 cm3 was also a significant risk factor for post-tonsillectomy hemorrhage. It is concluded that older age, a history of chronic tonsillitis, excessive intraoperative blood loss and elevated postoperative mean arterial pressure are significant risk factors for post-tonsillectomy hemorrhage. An awareness of these risk factors can help identify patients with potential to bleed postoperatively.