[en] Thyroid scanning with sup(99m)Tc-pertechnetate has been widely used as first choice, for the morphological examination of the thyroid, especially of the thyroid nodule, because of marked reduction in the radiation exposure to the thyroid and less time consumption than ¹³¹I-iodide. Twenty-two patients who were scanned with both sup(99m)Tc-pertechnetate (1 mCi to 2 mCi administered) and ¹³¹I-iodide (100 μCi to 200 μCi administered) within one month from January, 1974 to January, 1975 have been presented here. The authors found that: thyroid scanning with ¹³¹I-iodide is better in eighty-three percents of patients with low twenty-four hour ¹³¹I-uptake; both sup(99m)Tc-scan and ¹³¹I-scan are equal in scanning value in hyperthyroidism. sup(99m)Tc-scan is more variable in the scanning quality than ¹³¹I-scan; and ¹³¹I-scan is excellent for the early post-operative management of thyroid cancer, for the visualization of the remnant thyroid and for metastatic lymphnodes in the neck. Previous reports which had described different dosages of the radioiodide, and which had evaluated the diagnostic uses of sup(99m)Tc- on ¹³¹I-scans differently in hypothyroidism were not discussed. The authors found that in low RAIU, they had better results with ¹³¹I when 100-200 μCi of the radioiodide were administered. (Evans, J.)