In 1949 we reported our experience with thiourea derivatives in the treatment of nine children with hyperthyroidism due to diffuse toxic goiter and were impressed by the remissions obtained in five of these treated successfully.1 Their ages were 9, 11, 9, 5, and 13½ years and they were treated continuously for 13, 12, 7, 15, and 6 months, respectively. Subtotal thyroidectomy was performed on four of the nine patients, for the following reasons: (1) marked enlargement of the thyroid, although the patient was euthyroid after five months of treatment *; (2) refractoriness to the drug during treatment following a third relapse; (3) slow response to the drug in a child who had psychotic episodes and cardiac complications, and (4) poor cooperation from a badly disturbed child. Thus, only one case can be considered a drug failure. Because a great deal of controversy exists as to the advisability of prolonged treatment