Subclinical thyroids disease (STD) is recently defined term in clinical thyroidology, which includes mainly functional disorders. Basic diagnostic signs are: normal values of thyroid hormones (fT4, fT3) and elevated TSH level (subclinical hypothyroidism) or suppresed TSH level (subclinical hyperthyroidism). In a category of STD may be included subclinical autoimunne thyroiditis (elevated level of thyroid antigens antibodies and/or hypoechogenity in sonographic screen, increased volume of the thyroid without clinical symptoms and/or autoimminity) and microscopic lesions of papillary thyroid carcinoma. Subclinical hypothyroidism may be dangerous for tendency to development of manifest hypothyroidism and for risk of disorders of lipid profile and development of atherosclerosis and its organ complication (esp. myocardial infarction). Subclinical hyperthyroidism is a risk factor of cardiac arythmias and probably can increase a risk of cardiovascular mortality) as well for osteoporosis (esp. in peri- and post-climacteric women), and last but not least for degenerative diseases of brain (?). Indication of treatment of STD is a matter of controversies. Recomendations of experts, varied from "no therapy, monitoring only" to "treat always". Treatment of risk groups (esp. pregnant women) is probably nowadays a most rationale recommendations since results of sofisticated prospective studies will be available.