To determine whether the incidence of unrecognized thyroid disorders is high enough to warrant screening, we studied a group of 95 elderly hospitalized women with the use of clinical examinations, along with thyroid function tests. We found that 13 (13.7%) of the 95 women had elevated serum thyroid-stimulating hormone (TSH) levels and mean serum thyroxine (T4) levels, and their free T4 indexes and triiodothyronine levels (measured by radioimmunoassay) were lower than the levels in the normal control group. In four (4.2%) of the 95 patients, the elevation of TSH levels was transient. In two patients (2.1%), the elevation of TSH levels was caused by underlying hypothyroidism. The results of thyroid function tests, including serum TSH, obtained during acute nonthyroidal illness should be interpreted cautiously, and screening for thyroid disorders among elderly patients with acute illnesses is not warranted. While primary hypothyroidism may be regularly associated with an elevated TSH level, an elevated TSH level may be the result of an acute illness and not associated with clinical hypothyroidism.