Objective: The safety of day-case tonsillectomy is widely documented in the literature; however, there are no evidence-based guidelines recommending patient characteristics that are incompatible with day-case tonsillectomy. This study aimed to identify which patients should be considered unsafe for day-case tonsillectomy based on the likelihood of needing critical intervention.Method: Retrospective review of 2863 tonsillectomy procedures performed at University Hospital Geelong from 1998 to 2014.Results: Of the patients, 7.81 per cent suffered a post-tonsillectomy complication and 4.15 per cent required intervention. The most serious complications, haemorrhage requiring a return to the operating theatre and airway compromise, occurred in 0.56 per cent and 0.11 per cent of patients respectively. The following patient characteristics were significantly associated with poorer outcomes: age of two years or less ( p < 0.01), tonsillectomy indicated for neoplasm ( p < 0.01) and quinsy ( p < 0.05).Conclusion: The authors believe that all elective tonsillectomy patients should be considered for day-case surgery, with the following criteria necessitating overnight observation: age of two years or less; an indication for tonsillectomy of neoplasm or quinsy; and an American Society of Anesthesia score of more than 2.