The author presents a brief account of the clinically most important antibodies against thyroid antigens (against thyroglobulin, against the microsomal fraction or thyroid peroxidase, against thyroid hormones and against TSH receptors). He describes the main ways of their assessment in serum and evaluates the practical contribution of their estimation or detection in clinical diagnostic practice concerning endocrinopathies. Usually these estimations are only auxiliary and do not replace functional thyroid tests. Antibodies against thyroglobulin and against the microsomal fraction are found most frequently (and in the highest concentrations) in thyropathies with an assumed autoimmune component, in particular in lymphocytic thyroiditis. The low specificity (they are as a rule present also in other thyroid diseases and also in clinically eufunctional subjects with and without goitre) due to the relatively low prevalence reduce the diagnostic value of the examination. The examination of antireceptor antibodies is important, in particular in the diagnosis of immunogenic hyperthyroidism. The prevalence of antibodies against thyroid hormones is low and their detection serves about all to elucidate cases where the patient's clinical status is not in agreement with assessment of thyroid hormones.