Background: Mohs micrographic surgery (MMS) is distinguished from other techniques in that microscopic examination of all excised tissue occurs intraoperatively rather than after the surgery. Intraoperative frozen section (Fs) margin was immediately examined by pathologist and the permanent sections (Ps) were made and interpreted afterwards. Prompt procedure is the strong point of MMS, but it can make a gross sampling error or a misinterpretation of Fs. False negatives on Fs, that is, persistence of tumor at the margin can be attributed to provoke local recurrence. Objectives: To date,there were only few analyses between the results of Fs and Ps in patients treated with MMS. Therefore, we tried to refine the cause in patients showing different results between them. Methods: A retrospective analysis of 1141 patients with skin cancer treated with MMS between 1998 and 2013 was undertaken, investigating the resections and pathological analyses in a Pusan national universityhospital setting. All patients with a follow-up period of less than 1 year were excluded. Results: 269 of 1141 patients (23.6%) showed different results; negative margin on Fs and positive margin on Ps. But, only 3 patients (3/269, 1.1%) have been recurred. Conclusion: After a thorough analysis, the positive margin on Ps could not be a recurrence predictive factor in clinical fields. The reason for these results could be due to the surgical excision margin extremely close to the edge of tumor, that is, strong point of MMS.