Objective: Free tissue transfer is very popular for the reconstruction of defects in head and neck oncology.Although high success rate and good reliability of free flaps has been proven, microvascular thrombosis is still the most critical issue for microsurgeons.There are numerous protocols reported to prevent postoperative microvascular thrombosis but the efficacy is still debated.The aim of this study is to compare the outcome and complication of patients with and without postoperative anticoagulation.