Abstract: ObjectiveTo explore the change of serum estradiol(E2)and testosterone(T)concentrations throughout the puberty of girls and estimate the effects of genetic and environmental factors on serum E2 and T concentrations.Method The study population consisted of 180 pairs of twin girls aged 6 to 18 of whom.132 pairs monozygotic twins(MZ)and 48 pairs dizygotic twins(DZ),who were all from Qingdao city of Shandong province.Anthropometric measurement and pubertal development stage were determined by Tanner standard.Fasting serum E2 and T contents were assayed by Radioimmumo assay(RIA).ResultsSerum E2 and T concentrations increased from Tanner I toⅣand decreased later.E2 and T concentrations had substantial genetic variation,with additive genetic factors accounting for 40% and 47% of the total phenotypic variation,respectively.The heritabilities of E2 and T in post-menarche girls were greater than those of non-menarche girls.ConclusionSerum E2 and T concentrations of pubertal girls were influenced both by the genetic and environmental factors, and genetic influence on E2 was significant after menarche occurred.