Most effects of gonadal steroids on rat adrenal weight are indirect, depending upon alterations in the pituitary-adrenal axis for their expression. The direct effects of gonadal steroids on adrenal weight were studied using hypophysectomized castrated male rats receiving ACTH replacement, a model which excludes pituitary-adrenal feedback effects. Estradiol-treated rats did not differ from controls, whereas testosterone-treated rats exhibited a small but statistically significant decrease in adrenal weight. As a first step in exploring the mechanism of this androgen effect, a specific dihydrotestosterone-binding protein was identified in the rat adrenal gland. A single class of high affinity (Kd = 0.6-2.0 .times. 10-8 M), saturable (28 fmol/mg cytosol protein), cytoplasmic binding sites was found using both protamine sulfate precipitation and dextran-coated charcoal assays. The specificity, sedimentation coefficient on sucrose gradient, and sensitivity to sulfhydryl reagents and heat of this dihydrotestosterone-binding protein were typical of the cytoplasmic androgen receptor from other androgen target issues such as prostrate. Testosterone can decrease rat adrenal weight directly, and the mechanism may involve a high affinity binding protein, as has been shown in other androgen-responsive systems.