Maternal thyroid function was investigated in 29 pregnant women with goiter and 51 pregnant women without goiter in the eastern Black Sea region of Turkey, which is an endemic goiter area. Ten women with goiter and 10 healthy women without goiter were used as controls in the study. In all of the pregnant women, increased concentrations of total and free thyroxine, total and free tri-iodothyronine and thyroxine-binding globulin were found. Serum thyroid-stimulating hormone levels showed a decrease in pregnant women without goiter compared with non-pregnant women without goiter.