Thyroid antibodies against thyroglobulin, the microsomal fraction and TSH receptor have been investigated in 150 patients (41 of them with Graves'disease, 24 of them with Hashimoto thyroiditis, 21 of them with subacute thyroiditis and 34 cases with treated hypothyroidism). 30 patients having thyroid disease without immune etiology served as a control group. As compared with the control group, significant differences were detected in the titers of microsomal and TSH-receptor antibodies in Graves' disease, microsomal and thyroglobulin antibodies in Hashimoto thyroiditis, while significantly higher antibody titers were measured against the microsomal fraction antibodies in hypothyroidism. In subacute thyroiditis, no significant elevation of any of the three antibodies was demonstrated. The diagnostic values of antibodies were investigated; in Graves disease, the antibody against TSH receptor is the most sensitivity method (70%), while in Hashimoto thyroiditis the highest sensitivity (87,5%) is exhibited by the determination antibody against the microsomal fraction. The relationship between the thyroid hormone values and the antibody titer was investigated too. In Hashimoto thyroiditis with hypothyroid state significantly elevated microsomal antibodies were found, as compared with the euthyroid state. It may be concluded that in cases suspect of Graves disease, determination of antibody against of TSH receptor is recommended. In case of normal value, finding the antibody against microsomal fraction can confirm the diagnosis. In further conclusion, antibody measurements are rarely informative in subacute thyroiditis. In cases suspect of other thyroid diseases of immune origin, measurement of the antibodies against the microsomal fraction may be helpful, while the discriminative value of the thyroglobulin antibody is more limited.