Purpose: Free flap reconstruction is performed on defects including benign and malignant tumors as well as trauma in the department of oral and maxillofacial surgery, but there are few reports of free flap reconstruction cases for oral cancer in patients in Korea. Methods: This study was designed to retrospectively analyze surgical outcomes and complications of 164 free-flap reconstructions performed at the Oral Oncology Clinic, National Cancer Center, during 2002~2011. A total of 164 free flaps were performed for reconstruction of oral and maxillofacial defects which were caused by oral cancer and osteoradionecrosis in 155 patients. Results: The present study had 162 successful cases and 2 failed cases for a total of 164 cases. The study had a success rate of 98.8% for free-flap reconstructions. Flap donor sites included radial forearm free flap (n=93), fibula osteocutaneous free flap (n=25), anterolateral thigh flap (n=18), latissimus dorsi myocutaneous flap (n=16) and other locations (n=12). Postoperative medical complications were generally pneumonia and delirium. Postoperative local complications occurred including partial flap necrosis, delayed wound healing of the donor site, infection of the recipient site and salivary fistula. The incidence of postoperative complications and patient-related characteristics including age, sex, smoking, history of radiotherapy, hypertension (HTN) and diabetes Mellitus (DM) were retrospectively analyzed. Patient age ($P$=0.003) and DM ($P$=0.000) and HTN ($P$=0.021) were significant risk factors for complications overall. Conclusion: The present study had no mortality and confirms that free-flap reconstructions are extremely reliable in achieving successful results.