To describe the clinical characteristics and define the indicators that best predict survival in patients with bone metastases from thyroid carcinomas. We collected data from medical records of 146 patients with documented bone metastases from thyroid carcinoma seen at our medical center over a 38-year period. Univariate and multivariate analyses of prognostic indicators for survival were performed. Bone metastases were present at the initial diagnosis in 47% of patients. Vertebrae (29%), pelvis (22%), ribs (17%), and femur (11%) were the most common sites of metastases. Multiple lesions were present in 53% of the cases. The overall 10-year survival rate from the time of diagnosis of thyroid cancer was 35%, and from diagnosis of initial bone metastasis was 13%. By univariate analysis from the time of the initial bone metastasis, radioiodine uptake by skeletal metastases, the absence of nonosseous metastases and treatment with radioiodine were significant prognostic factors. By multivariate analysis, radioiodine uptake by skeletal metastases and the absence of nonosseous metastases were independent favorable prognostic variables for survival. In a subgroup of patients in which histologic specimens were available and were reviewed, Hurthle cell carcinoma was the most favorable histologic subtype for survival with the undifferentiated subtype being the worst. The spread of thyroid carcinoma to bone is more common in patients over 45 years of age, is usually symptomatic, and is often multicentric. Overall survival is best in those whose lesions concentrate radioactive iodine and those who have no nonosseous metastases.