Repeated cold exposure (4 degrees C) was followed an increase in the concentrations of total thyroxine, free thyroxine, and total triiodothyronine in blood plasma of male rats, while single cold exposure was accompanied by a significant increase only in the concentrations of total triiodothyronine and free thyroxine. After administration of dehydroepiandrosterone sulfate (30 mg/kg), the increase in total thyroxine and total triiodothyronine concentrations became more pronounced after repeated cold exposure, but not after single cold exposure. Dehydroepiandrosterone sulfate did not affect the concentration of free thyroxine after single and repeated cold exposure.