Abstract: The second generation female Wistar rats that have been treated with iodinedeficient food,after their delivery,are divided into three groups i.e.excessiveiodine(EI),adequateiodine(AI) and iodinedeficient(ID) according to the KIO3 concentration in the drinking water(3.0,0.4,0 mg/L). In addition,the normal rats with low iodine food and 0.4 mg/L KIO3 water are used as the control group (C).The iodine content in thyroid and the serum thyroid hormone levels of the third generation rats are measured by means of epithermal neutron activation analysis (ENAA),and the method of enzymelinked immunosoerbert assay (ELISA),respectively. The results indicate that the total thyroxine (TT4) and the free thyroxine (FT4) of the EI,compared with those of the controls,are significantly decreased (p<0.001),whereas the free triiodothyronine(FT3) evidently increased (p<0.001).The body weight of the third generation weanling rat of EI is seriously reduced and their thyroid is swollen,but the total iodine content in thyroid is not altered.There is no significant difference between AI and C in the thyroid weight,iodine content and serum hormone levels.This study also indicates that if mother rats suffering iodine deficiency in gestation period gets an adequate iodine intake soon after delivery,an normal iodine level would be found in the body of her baby rat.However,excessive iodine intake may result in low levels of TT4,FT4 and goiter.