Intrahypothalamic implants of testosterone propionate (TP), 5α-dihydrotestosterone (DHT) and estradiol (E) were compared for their effectiveness in reactivating sexual behavior of castrated male golden hamsters. Males tested preexperimentally and then observed for loss of sexual behavior responses after long-term castration were divided into four experimental treatment groups: anterior TP implants, DHT implants and E implants, and posterior TP implants. All animals were tested at 7 and 21 days postimplantation. On the day 7 implant test mount frequency, latency and duration per mount were significantly different from the castrate response for the TP implant groups. On the day 21 implant test both TP and E implant groups showed significant changes in mounting while intromission frequency, latency and duration per intromission were significantly different from the castrate only for the TP implant groups. DHT implants were not effective in reactivating any aspect of copulatory behavior in the castrate male hamster