The purpose of this study was to identify possible changes in thyroid functions in newborn infants of preeclamptic women. Fifteen neonates (nine boys and six girls) of preeclamptic women and 17 healthy neonates (nine boys and eight girls) for the control group were included in the study. Serum thyroid-stimulating hormone (TSH), total triiodothyronine (TT3) and total thyroxine (TT4) levels and thyroid gland volumes were determined in both groups. Serum TSH and TT4 levels were not statistically different between the two groups. However, serum TT3 level was 79.22 +/- 40.19 ng/dl in the study group and 40.00 +/- 15.99 ng/dl in control subjects (p<0.01). The mean right, left and total thyroid volumes were 1.3 +/- 1.2 ml, 1.2 +/- 1.1 ml and 2.4 +/- 2.3 ml in the study group and 0.6 +/- 0.2 ml, 0.6 +/- 0.2 ml, and 1.1 +/- 0.4 ml in the control group, respectively (p,0.05). The mean thyroid volume/body weight was 0.9 +/- 0.09 ml/kg in the study group and 0.3 +/- 0.06 ml/kg in the control group (p,0.05). In conclusion, we would like to stress that preeclampsia might be a cause of fetal and neonatal thyroid enlargement and elevated serum TT3 level.