This is a retrospective review of 6842 tonsillectomies and adenoidectomies performed over a seven-year period at the Montreal Children's Hospital. The total incidence of postoperative bleeding was 2.5%. The incidence of primary post-tonsillectomy hemorrhage was 1.0%, with 78% of these children having developed bleeding within 12 hours of surgery. The overall incidence of secondary post-tonsillectomy hemorrhage was 1.2%. Twenty-nine percent of children with primary hemorrhage required a second general anesthetic, and 40% required blood component transfusion. Eight percent of children with secondary hemorrhage required a second general anesthetic and 24% received transfusions. Based on these findings, primary and secondary hemorrhage can be classified further into major and minor. The criteria for a major post-tonsillectomy hemorrhage are: requirements of a general anesthetic to control and repair the bleeding, or blood loss that is sufficient to require blood component transfusion therapy. The relevance of these findings with regard to outpatient adenotonsillectomies is discussed.