Abstract
Female golden hamsters are unusual both in the high levels of aggression they exhibit on nonestrous days of the estrous cycle and in the dramatic decrease in aggressiveness apparent on estrous days. The results of studies using adrenalectomized-ovariectomized or hypophysectomized females have failed to reveal any individual ovarian or pituitary hormone that is required for the display of high levels of aggression. In contrast, it seems clear that a very specific combination of ovarian hormones normally accounts for the inhibition of fighting and stimulation of sexual receptivity seen on estrous days.