Objectives: To investigate if a single dose of betamethasone given perioperatively could reduce common post-operative problems such as vomiting, nausea and pain in children undergoing tonsillar surgery. Background: Post-operative nausea and vomiting (PONV) are common problems after surgery caused by several perioperative factors, such as post-operative pain. Prophylactic treatment of PONV can be effective in improving recovery after surgery. Studies have shown that the use of a single dose of dexamethasone during tonsillectomies in children was efficient against PONV. Dexamethasone is not available in Sweden for intravenous administration; betamethasone was thought to be an alternative. Method: The study was a retrospective cohort study including 69 children who underwent tonsillar surgery. A single dose of betamethasone perioperatively was introduced to a group of 32 children, to reduce PONV while 37 children did not receive betamethasone. Data were received from the medical records and from a postoperative questionnaire.Results: No significant differences for children undergoing tonsillar surgery regarding the prevalence of PONV between the betamethasone group and the non-betamethasone group were found. This was maybe due to a comparatively low dose of betamethasone. However, the given dose was sufficient to significantly reduce postoperative pain.