Subclinical hypo and hyperthyroidism are asymptomatic disease of thyroid gland which can be detected only with laboratory tests. The changes are seen on plasmatic levels of thyroid hormones. The incidence of subclinical thyroid gland diseases varies among populations and for subclinical hypothyroidism ranges from 3 to 15%, and for subclinical hyperthyroidism of 3-10%, with a higher incidence associated with increasing age, female sex, and a suboptimal iodine status. The risk of progression of subclinical hypothyroidism to overt hypothyroidism is approximately 2 to 6% per year; the risk is higher among women than among men and among persons with higher thyrotropin levels, those with higher levels of antibodies to thyroid peroxidase, and those with low-normal free T4 levels. The best predictor of progression from subclinical hyperthyroidism to overt hyperthyroidism is the baseline serum thyrotropin level, lower the TSH, higher the possibility of this progression.The aim of this study is to evaluate laboratory data of subclinical hypothyroidism and hyperthyroidism on outpatients, their frequencies, gender and age distribution and their causes.