Thyroid microcarcinoma(TMC) is defined by the World Health Organization as carcinoma 1.0cm or less in its greatest dimension. TMC is being found in an increasing proportion of treated thyroid carcinomas due to the more frequent use and the technical improvement of ultrasonography and fine needle aspiration biopsy. Clinicians should be aware of the differences between TMC and clinical thyroid cancer (more than 1cm in diameter) when making a surgical decision. The aims of this study are to characterize the clinical and biological behaviors of TMC, to demonstrate the prognosis according to the risk factors and treatment modality, and to suggest a proper surgical management of TMC.