Tonsillectomy is a frequently performed surgical procedure in children and adults. Postoperative bleeding is the most severe complication; however, the factors leading to postoperative haemorrhage are still discussed controversially. 1,522 tonsillectomies were retrospectively reviewed. Histopathological tonsil composition was correlated with the incidence of postoperative haemorrhage. Patient charts were analysed with regard to demographic data, characteristics of postoperative haemorrhage and indication for surgery. Patients with post-tonsillectomy haemorrhage were compared with uneventful cases. Histopathological signs of cryptic tonsillitis and actinomyces infection displayed a statistically significant correlation with the risk of postoperative haemorrhage (P = 0.018 and P = 0.02), but the odds ratio was low (1.9 and 2.0). 7.7% of all patients had postoperative bleeding and 3.5% had to return to theatre for haemostasis. The incidence of haemorrhages within hospitalization (5 postoperative days) was 45% and after discharge 55%, respectively. In 11% of cases bleeding occurred on the fourth or fifth day after surgery. While gender, season of surgery, abscess tonsillectomy "en chaud" in comparison with elective tonsillectomy were not associated with an increased rate of postoperative haemorrhage (P > 0.05), significant more postoperative haemorrhages were detected in the group of adults (P = 0.02). Despite significant correlation of cryptic tonsillitis and actinomyces infection with postoperative haemorrhage, the risk for postoperative bleeding is only slightly elevated and, therefore, the predictive value is low. Because a multifactorial aetiology of post-tonsillectomy haemorrhage has to be assumed, large multicenter studies are necessary to evaluate the significance of different risk factors.