Hyperthyroidism may be defined as those clinical conditions which result from an increase in the circulating levels of one or both thyroid hormones. Hyperthyroidism in broad sense could be classified with toxic diffuse goiter, toxic adenomatous goiter, and toxic multinodular goiter on the basis of the circulating thyroid hormone levels. For this study, the subject included 94 cases with hyperthyroidism were presented in 77 with toxic diffuse goiter, 8 with toxic adenomatous goiter, and 9 with toxic multinodular goiter on the levels of 125IT3 resin uptake rate and serum thyroxine (T4). The observed results were as follows: 1) In the cases of hyperthyroidism including toxic diffuse goiter, toxic adenomatous goiter, and toxic multinodular goiter, 20.21% of the patients were male and 79.79% female. The majority of the patients were in 2nd to 4th decades of their lives. 2) There were objective signs clearly manifested in hyperthyroidism including toxic diffuse goiter and toxic adenomatous goiter which were rare in the multinodular goiter. The clinical signs in toxic diffuse and toxic adenomatous goiter included wide pulse pressure, tachycardia, systolic murmur, exophthalmos, tremor and warm skin etc. (Table 3.) 3) The most freauent complaints of the patients with hyperthyroidism were palpitation, weight loss, increased appetite, perspiration, heat intolerance, nervousness, exertional dyspnea, and menstrual disturbance etc. (Table 4.) There was no clear difference in the incidence of symptoms between toxic diffuse goiter and toxic adenomatous goiter, but there was clear difference between toxic multinodular goiter. 4) Considering of results of 125IT3 resin uptake rate and serum T4 level in toxic diffuse goiter, toxic adenomatous goiter and toxic multinodular goiter, 125I T3 regin uptake rate was 49.15¡¾9.94% (mean) and serum T4 21.29¡¾7.04 ug/dl (mean) in toxic diffuse goiter. In toxic multinodular goiter, 125I T3 resin uptake rate was 32.47¡¾6.74% (mean) and serum T4 level 11.03¡¾5.0 ug/dl, and then there was clear difference in the results of 125I T3 resin uptake rate and serum T4 between toxic diffuse goiter and toxic multinodular goiter. The levels of 125I T3 uptake rate and serum T4 in toxic adenomatous goiter were 40.32¡¾13.08% (mean), 15.47¡¾8.25 ug/dl (mean) respectively, so there was no clear difference between toxic diffuse goiter and toxic adenomatous goiter. 5) There was no significant differnece in length and width performed width thyroid scanning in toxic diffuse goiter, toxic adenomatous goiter, and toxic multinodular goiter.