A castration technic was perfected for removing seminiferous tubules and Leydig cells from the tunica albuginea, leaving the epididymis and its nerve and vascular supplies intact. There was a significant decrease in seminal vesicle weight in 15 guinea pigs castrated by this new procedure, indicating that the testicular androgen source was removed during castration. Spermatozoa remained motile in the ductus deferens of 18 animals that had been castrated for periods ranging from 7-70 da. The longevity of spermatozoa in the excurrent ducts was attributed to minimal trauma and damage to the ducts and their vascular and nvere supplies using this new technic.