To date there exists no sensible way of classifying the intensity of haemorrhage following tonsillectomy, though this is a prerequisite when comparing the results presented in literature. We evaluated the incidence of post-operative haemorrhage according to our classification in 602 patients who underwent tonsillectomy at our department in 1999. In 21 patients a grade 1 (spontaneous cessation) bleeding occurred. One patient had a grade 2 (infiltration anaesthesia), 14 patients had a grade 3 bleeding (treatment under general anaesthesia) with one patient receiving a blood transfusion. Two patients had a grade 4 bleeding (ligature of the external carotid artery). There was no patient with grade 5 bleeding (lethal outcome). Grades 1 and 3 had the same incidence rates. Primary haemorrhage (<24 hours) can be expected in the majority of patients undergoing tonsillectomy. Secondary haemorrhage is rare and can be life-threatening.