The purpose of the study was to investigate whether testosterone and estradiol effects on rat adrenal cortex are mediated by the thyroid gland. Experiments were performed on gonadectomized rats, some of them underwent also surgical thyroparathyroidectomy (TPX). In appropriate groups animals were treated with testosterone or estradiol and thyroxine. The following parameters of the adronocortical function were estimated: weight of the adrenal gland, corticosterone production by adrenal homogenate and slices, sensitivity of slices to ACTH, adrenal 5 alpha-reductase and 11 beta-hydroxylase activities and serum corticosterone level. Obtained results suggest that estradiol effects on adrenal glands weight and their responsiveness to ACTH were partially mediated by the thyroid gland. On the contrary, thyroid gland was not involved in testosterone evoked changes in function of the rat adrenal cortex.