The present study was carried Out to investigate the effects of 4-tert-octylphenol (OP) exposure at fetal period oil adrenal, pituitary, thyroid + parathyroid and pancreas tissues of male and female offsprings. Pregnant rats were treated with OP (100 or 250 mg/(kg day)) in vehicle (corn oil) or vehicle alone daily from day 1 to 20 of pregnancy. After birth, young rats were allowed to growth until adulthood. While there were no differences in data of organ weight between control and treatment groups, in contrast, a decrease of relative organ weights of thyroid + parathyroid and adrenal in high close treatment group in male rats, otherwise an increase of final body weights was found in 250 mg/(kg day) treatment group in all rats. Also, a lot of histopathological findings were observed in investigated tissues. The results of this study Suggest that, the octylphenol which was applied in fetal period causes negative effects on the adrenal, pituitary gland, thyroid + parathyroid and pancreas in rats. (C) 2008 Elsevier B.V. All rights reserved.