Despite the large number of tonsillectomies performed little knowledge exists about post-tonsillectomy hemorrhage (PTH) with lethal outcome. This study was performed to evaluate clinical features in a larger patient population with emphasis on the onset of this complication. A nationwide collection of cases was performed based on personal communication, expert reports to lawsuits and professional boards, and case reports received after a plea published in a professional national journal. Clinical data of 29 patients were collected of whom the 18 were children (64%). With one exception all patients experienced secondary PTH (>24 h) occurring 1-28 days after tonsillectomy. Aspiration contributed to lethal outcome in 13 cases. Fatalities were unavoidable although 21 patients were in the hospital. Massive vomiting of blood was observed in 11 patients. There were 11 patients without (group A) and 18 with (group B) episodes of repeated bleeding. This study suggests that particularly children are endangered by lethal PTH. Inpatient treatment was unable to prevent lethal outcome in this selected patient population. However, it appears wise to re-admit patients with delayed PTH, since excessive PTH may occur. These unexpected and unpredictable situations require an immediate and adequate medical treatment by a skilled staff. The paucity of data currently does not allow calculation of a cut-off point at which the risk of life-threatening PTH significantly decreases. Secondary PTH remains a substantial complication.