Turner's syndrome was originally reported as sexual infantilism, short stature, webbed neck and cubitus valgus. Subsequent investigations, however, have disclosed many other abnormalities both in chromosomal and physical features occurring in this syndrome. An increased prevalence of Hashimoto's thyroiditis in patients with Turner's syndrome has been well documented and molecular defects of the TBG have been described. In our study we examined serum T3, T4, FT3, FT4, TSH and TBG levels in 18 girls with Turner's syndrome, in 18 healthy control girls and in the parents of both groups. We reported significant elevated levels of T3 and FT3 in the Turner's group (P 0.01). We did not find any quantitative abnormalities of immunoreactive TBG in the same patients.