FSH receptor has been shown to be specifically expressed only in the Sertoli cells in males. In one of our studies that consisted of deprival of endogenous FSH in immature rats and adult bonnet monkeys, atrophy of the epididymis was observed, cauda region being the most affected. Although epididymis is an androgen-dependent tissue, the changes in histology of the cauda region were observed without any associated change in the levels of testosterone in FSH-deprived animals. Considering this, it was of interest to evaluate the possibility of epididymis being a direct target for FSH action. In the present study, we have examined the expression of FSH receptor in the epididymis of rat and monkey. In the cauda region of rat epididymis, FSH receptor expression was demonstrated by RT-PCR and Northern and Western blot analyses. FSH receptor was found to be functional as observed by its ability to bind ¹²⁵IoFSH, by an increase in cAMP production, and by BrdU incorporation following addition of FSH under in vitro conditions. These results suggest the possibility of a role for FSH in regulating the growth of the epididymis.