Clinical measurement of thyroid autoantibodies in sera of some thyroid disorders have been widely applied since about twenty years ago, We investigated the incidence and titers of both antimicrosomal and antithyroglobulin antibodies in forty eight cases with controls and one hundred and thirty three patients with some form of thyroid disorders. The results were as follows; 1) In controls, antimicrosomal antibodies were positive in 2% but antithyroglobulin antibodies were all negative. 2) In a series of one hundred and thirty three patients with thyroid disease, antimicrosomal antibodies were positive in 44% but antithyroglobulin antibodies were positive in only 15%. 3) The rate disclosing the positive results of antimicrosomal antibodies were 71% in Hashmoto's disease, 60% in Graves' disease, and 38% in primary hypothroidism, respectively. On the other hand, the positive results of antithyroglobulin antibodies showed 21% in Graves' disease, 19% in primary hypothyroidism, and 18% in Hashmoto's. disease, respectively. Though there were relatively high rate of both antimicrosomal and antithyroglobulin antibodies in patients with nodular goiter, they were only seven cases in our series. 4) The rate with the extremely high titers of antimicrosomal and antithyroglobulin antibodies (〉:1602) was 83% and 67% in Hashmoto's disease, 50% and 67% in primary hypothyroidism, and 41% and 18% in Graves' disease. Accordingly, the thyroid autoantibodies, were commonly found higher positive rate in patients with Hashmoto's disease, primary hypothyroidism, and Graves' disease. Among these disorders, the extremely high positive rate of the thyroid autoantibodies was found in patients with Hashmoto's disease.