Background and Objectives: Brain metastasis from well-differentiated thyroid carcinoma is uncommon, and the treatment remains controversial. In this study, we analyzed cases of brain metastasis from well differentiated thyroid carcinoma to determine optimal treatment. Material and Methods: From March 1986 to May 2003, we experienced 13 cases of brain metastases from well-differentiated thyroid carcinomas. There were 6 men and 7 women with a mean age of 62.3 years. The time interval detecting the brain metastasis, treatment methods, outcomes, and the prognostic factors were analyzed. Results: In 11 patients, brain metastasis was found at a mean of 96 months after thyroid surgery (range, 1-204months). In 1 patient, brain metastasis was found simultaneously with the thyroid cancer. In the remaining one, brain metastasis was presented as the first sign. Treatment included gamma knife therapy in 2, external radiation therapy (ExRT) in 2, resection and ExRT in 2, gamma knife therapy and ExRT in 2 and intracranial holmium injection in 1. Three patients received no treatment. The mean survival was 20.5months (1-119 months). Only 2 patients with early detection remained alive after treatment (23months and 119months). The age, sex, primary tumor size, combined organs of distant metastasis and treatment methods did not affect the prognosis. There were noticeable symptomatic improvements in patients who received any kind of treatment for brain metastasis. Conclusion: Early detection and treatment of brain metastasis appears to bring symptomatic relief and improve survival. Therefore, early screening for brain metastasis is recommended for patients with symptoms. However, further study is needed to determine the optimal method of treatment.