Testosterone and dihydrotestosterone3 receptor proteins were studied in normal rats and mice and compared to those in animals with testicular feminization, an inherited end organ insensitivity to androgens. Androgen binding proteins (7.5s), similar to that in prostate, were demonstrated in cytosol from normal rat preputial gland and mouse kidney. There were, however, no demonstrable specific androgen receptors in cytosol from insensitive animals. We postulate that this deficiency of cytosol androgen receptor precludes androgen transfer to the nucleus of the cell resulting in the androgen insensitivity of testicular feminization.