This study was aimed to evaluate the effect of the use of Platelet- Rich Fibrin on immediat complication following impacted mandibular third molar surgery. forty extractions of bilateral impacted mandibular third molars were performed in 20 volunteers (18 to 25 years old). After extraction of right and left mandibular third molars, the socket at 1 side received the autologous PRF (test group) and the other was filled with blood clot (control group) .