We have reviewed our experience with the management of patients with thyroid cancer to assess the potential benefits of employing the serum thyroglobulin assay in patient management programs and to determine the optimal conditions for this application. Serum thyroglobulin levels were found to be more reliable when obtained from hypothyroid patients. Levels of thyroglobulin greater than 10 ng/mL appeared to be abnormally elevated in both thyroidectomized patients prior to radioactive iodine therapy (group 1) and in thyroidectomized patients after radioactive iodine therapy (group 2). Elevated thyroglobulin levels were found to be useful indicators of the presence of metastatic disease, whereas normal thyroglobulin levels were reliable indicators of the absence of metastases. In group 1 patients, elevated thyroglobulin levels reliably predicted the presence of important total body scan uptake. In group 2 patients, normal thyroglobulin levels reliably predicted the absence of total body scan uptake. The serum thyroglobulin assay can substantially reduce the need for repetitive total body scanning in the follow-up of group 2 patients with thyroid cancer.