From a multivariate analysis of more than 20,600 patient-years' experience with papillary thyroid carcinoma (PTC), we devised a prognostic scoring system based on patient age, tumor grade, extent, and size (AGES). This scoring system was used as an adjustment variable for analyzing the role of different types of surgical treatment in the development of local recurrence (LR) in 963 PTC patients who underwent unilateral (15%), bilateral subtotal/near-total (69%), or total thyroidectomies (16%) from 1946 through 1975 at the Mayo Clinic. In 866 patients with AGES scores of 3.99 or less, the risk of LR developing at 10, 20, and 30 years was 7%, 14%, and 14% after unilateral resection and 1.5%, 2%, and 4% after bilateral resection (p less than 0.001). In 97 patients with AGES scores of 4 or more, the comparable rates were 26%, 45%, and 59% after unilateral resection and 13%, 20%, and 20% after bilateral resection (p less than 0.001). In neither the low- nor the high-risk group was there a significant difference in the frequency of LR comparing total thyroidectomy with bilateral subtotal/near-total thyroidectomy. At 30 years after diagnosis of LR, mortality from PTC was 48%; the risk of cancer death with an LR located outside the thyroid remnant was much greater than with a remnant recurrence alone. In this series of 52 patients, followed up for as many as 41 years, no patient with tumor recurrence limited to the thyroid remnant died of thyroid cancer.