2,512 consecutive patients with papillary thyroid carcinoma (PTC) were managed during 1940 through 2000 at the Mayo Clinic. During that period, there were two significant therapeutic trends. The first was a change in surgical practice during 1940-69 from an initial unilateral lobectomy (UL) to a bilateral lobar resection (BLR). The second was the increasing use since 1970 of I-131 for radioactive-iodine remnant ablation (RRA). The advent of BLR resulted in significantly improved tumor recurrence (TR) rates in both low-risk (MACIS scores < 6) and high-risk (MACIS scores 6+) patients, and also reduced cause-specific mortality (CSM) in high-risk patients. By contrast, RRA did not significantly improve the outcome (either CSM or TR) in low-risk (MACIS < 6) patients previously treated with initial near-total or total thyroidectomy. These data encourage a more selective use of I-131 in PTC management and do not lend support to the current widespread use of RRA in low-risk PTC.