Objective: To evaluate the effect of preoperative versuspostoperative administration of oral Dexamethasone on postoperativecomplications including pain, edema and trismus following lowerthird molar surgery.Methods: 24 patients were divided into two equal groups receiving8mg Dexamethasone orally, one group by one hour preoperativelyand the other group immediately after surgery.Results: Although in this study pain and trismus records werecomparable and statistically non-significant in both groups; theresults has proven that preoperative oral administration of 8 mgDexamethasone was superior to the postoperative administrationconcerning the edema after lower third molar surgery.