Background: Post-operative nausea and vomiting (PONV) still is a common and undesired problem after general surgery and is depended by several factor such as age, sex and type of surgery. The aim of this study is to compare effect of dexamethasone with severe hydration on PONV after elective tonsillectomy. Material and Methods: Seventy-seven patients scheduled for non-emergency tonsillectomy enrolled in a prospective double blind randomized clinical trials. All the patients received two milliliters per kilograms body weight ringer solution for every hour fasting. Control group received four milligrams dexamethasone and the case group received twenty milliliters per kilogram body weight ringer solution before surgery. PONV was noted and recorded in recovery and surgery units. Results: There was no difference between groups regards to blood pressure, heart rate, and PONV. The incidence of PONV in case group and control group was 25.6% and 26.7% respectively (P value>o.o5). Conclusion: Severe hydration can be a safe and available alternative for dexamethasone in prevention of PONV after tonsillectomy.