목적: Current guidelines (NCCN Clinical Practice Guideline in Oncology, Head and Neck Cancer, Version 2014) recommend the intensified adjuvant treatment in case with close surgical margins (-5mm) (CM) in patients with oral squamous cell carcinomas (OSCC) in spite of tumor size or stage. Thus, we aimed to determine the differential impact of CM on local recurrences in relation with primary tumor sizes of OSCC. 방법:Clinical and pathological characteristics of 325 patients having surgery for their OSCC of the tongue, floor of the mouth and cheek were retrospectively analyzed. Variables included margin status (negative, close, positive margin), primary tumor size, nodal metastasis, histological parameter (tumor grade, lymphovascular invasion, peri-neural invasion), and adjuvant therapy or re-resection. Cox proportional hazards models and Kaplan Meier analyses were used to determine the relative impact of resection margin status on local recurrences in patients stratified into early (T1-2) versus advanced stage (T3-4) OSCC. Results of detailed pathological evaluations will be presented. 결과:Overall, local recurrences were significantly higher in patients having positive surgical margins (p = 0.003, HR = 18.704, 95% CI = 2.662-131.395), while not increased in patients having CM. When the patients were stratified into small (T1-2) and large (T3-4) tumors, CM was a significant risk factor for local recurrences in T3-4 OSCC (p = 0.036, HR = 11.079, 95% CI = 1.170-104.863), but not in T1-2 OSCC. In T3-4 OSCC, post-operative adjuvant therapies significantly decreased the recurrence rates (p = 0.009 in radiation therapy, p = 0.025 in chemo-radiation therapy). 결론:CM was not an independent risk factor of local recurrences in T1-2 OSCC while it significantly increased local recurrence rates in T3- 4 OSCC. Positive resection margin was an important risk factor for local recurrences regardless of primary tumor size.