Data for patients with bone metastases (BMs) of differentiated thyroid carcinoma (DTC) were retrospectively studied to identify fac- tors associated with survival. We especially studied the impact of therapies. Among the 1977 patients followed for DTC in our depart- ment from 1958 to 1999, 109 (77 females and 32 males; age range, 20 - 87 yr) presented BMs. All patients except 1 underwent total thyroidectomy, followed by radioiodine therapy ($3.7 gigabecquerels) in 95 cases. Survival rates at 5 and 10 yr were 41% and 15%, respec- tively. Univariate analyses indicated that a young age at BM discov- ery (P , 0.005) and the discovery of BM as a revealing symptom of DTC (P , 0.05) were features significantly associated with improved survival as well as radioiodine therapy (P , 1024) and BM complete surgery (P , 0.02). Using multivariate analysis, the detection of BMs as a revealing symptom of thyroid carcinoma (P , 0.0005), the ab- sence of metastasis appearance in other organs than bones during the follow-up (P , 0.03), the cumulative dose of radioiodine therapy (P , 0.0001), and complete BM surgery in young patients (P , 0.04) ap- peared as independent prognostic features associated with an im- proved survival. (J Clin Endocrinol Metab 86: 1568 -1573, 2001)