Background. First described 9 decades ago by H. S. Plummer, thyroidectomy and radioiodine remain the 2 therapeutic modalities for toxic nodular goiter. The aim of this study was to determine its optimal treatment. Methods. The presentation, operative treatment, pathology, and clinical course, of 362 consecutive patients treated at our institution for Plummer's disease from 1990 to 1999 were retrospectively reviewed. Results. Three hundred forty-six patients (63 men and 283 women) were treated surgically (181, 53%), with radioiodine (RAI, 15 7, 45%), or a combination of both (8, 2%). Mean age was 62 years (surgical, 55 years; RAI, 69 years). Nearly half were symptomatic, 51 (15%) with airway or swallowing compromise and I 10 (32%) with cardiac complications. The estimated goiter size was larger (60 g or. greater) in surgical (72 patients, 38%) than medically treated (45 patients, 29%) patients. RAI treatment dose averaged 28 mCi; 10 patients (6%) required a second treatment, and 8 patients failed treatment and required subsequent thyroidectomy. Types of thyroidectomy included total (29 patients, 16 near-total (4 7 patients, 26%), bilateral subtotal (46 patients, 25%), and unilateral (58 patients, 32%). One month after treatment, hyperthyroidism had resolved in 96% of the surgical patients but only 6% of the RAI patients (mean time to resolution, 5.4 months). Only 55 (38%) of the RAI patients' goiters reduced in size. Recurrent laryngeal nerve paralysis and hypoparathyroidism each occurred in 3 (2%) patients. Conclusions. Surgical treatment results in rapid, reliable resolution of. hyperthyroidism and removal of the nodular goiter with low morbidity and no mortality. RAI is also safe and effective, usually requiring a single dose, but the results are delayed and it usually fails to resolve a goiter.