Subclinical thyroid disease is usually used to describe patients with mild symptoms correlated to hyperthyroid or hypothyroid state. Thyrotropin (TSH, thyroid stimulating hormone) is the pivotal investigation in laboratory diagnosis to define subclinical thyroid diseases. An elevated TSH with normal free thyroxine and triiodothyronine levels in serum is defined to be subclinical hypothyroidism, and a subnormal TSH with normal thyroid hormone concentrations to be subclinical hyperthyroidism. Generally, the prevalence of subclinical hypothyroidism and hyperthyroidism were reported as 4% -10% & 1%-2% in general population, respectively. Although subclinical thyroid disease is prevalent, there is still no consensus for screening such disorders under consideration of age, gender or familial history of autoimmune thyroid disease. However, screening for thyroid dysfunction should be considered in some high risk patients, including 1) elderly; 2) history of atrial fibrillation; 3) previous thyroid disease history; 4) other confirmed autoimmune diseases; 5) neck exposure of radiation (for example, nasopharyngeal cancer, postradiation); 6) family history of probable autoimmune thyroid disease, and 7) pregnant state with prior thyroid disease history. Therapeutic decision for such subclinical thyroid dysfunction should be considered individually. For subclinical hyperthyroidism, treatment strategies are usually based on TSH levels, risk of progression to overt hyperthyroidism, clinical symptoms, and concurrent cardiac diseases. Therapeutic options will be anti-thyroid medications and/or radioactive iodine, and thyroidectomy could be considered with larger goiters. For subclinical hypothyroidism, the therapeutic consideration should be aimed on reduction of progression to overt hypothyroidism, improving heart function, correction of dyslipidemia, and relieving senescence depressive mood. But long term outcome for treatment of subclinical thyroid disease is diversified, especially in the field of subclinical hypothyroidism. Further investigations should be observed in the future.