The effect of testosterone and its active metabolite 17β-hydroxy-5α-androstan-3-one (dihydrotestosterone) on the sexual behavior (mating and mounting) of ovariectomized rabbits was tested. Subcutaneous injections of 250 μg of testosterone propionate twice daily for 5 days induced mating in all the subjects tested and mounting in 50% of them. Dihydrotestosterone propionate at various dosages (1, 2, 6.5 and 10 mg twice daily) failed to stimulate sexual behavior in 4 groups of rabbits. Implants of dihydrotestosterone propionate into the ventral hypothalamus did not elicit either mating or mounting in ovariectomized rabbits. The results suggest that the reduction of testosterone to dihydrotestosterone is not essential for the production of estrous behavior in the rabbit. (Endocrinology86: 939, 1970)