In order to investigate the influences of acute hemorrhage on the motility of non-pregnant uterus, bleeding amounting 1.5-2.0% of the body weight was performed in the adult female rabbits and the intrauterine pressure was recorded prior to and 20 minutes after the bleeding. The animal were divided into four groups. They were; Group 1. 10 rabbits with intact ovaries. Group 2. 5 rabbits oophorectomized, 3 weeks before recording and without hormonal treatment. Group 3. 5 rabbits oophorectomized, and 2 weeks later estrogen was given 25 g/kg daily for 1 week. Group 4. Progesterone was also given 0.5mg/kg daily, otherwise the protocol was same as in group 3. The intra-uterine pressure generated by the contraction of the uterine musculature was recorded through the polyethylene tubing inserted in the uterus which was surgically exposed. Through the tubing, constant flow of saline solution was secured by an infusion pump, and the pressure was transmitted to the pressure transducer via the liquid column. The area beneath the pressure curve in the recording paper represented the magnitude of the pressure impulse (integral) in finite period. The frequency of the uterine contraction was expressed as the counting of wave in 5 minutes. Records were also taken 20 minutes after transfusion of the shed blood. The results obtained were as follows; 1. In the animals with intact ovaries, acute hemorrhage resulted in the decrease of the intra-uterine pressure impulse (integral) by 22% on the average. However, the frequency of the contraction increased as much as 14% above the value obtained before hemorrhage. Those responses were interpreted as the consequences of the enhanced activities of the sympathetico-adrenomedullary system. By re-transfusion of own shed blood the alterations in the pressure impulse and the frequency of contraction were partially restored. 2. In the oophorectomized rabbits without hormonal replacing therapy, the uterine activities were rather quiescent in general and the alterations in acute hemorrhage were also scanty. 3. The motility of the uterus of the oophorectomized animal was completely restored by the administration of estrogen, alone or combined with progesterone, for one week. Here it was reaffirmed that hormonal support was necessary for the responses of the uterine motility to the acute hemorrhage the hormonal support was required. 4. By the combined treatment of estrogen and progesterone, the uteri of the oophorectomized animals showed less motility compared with the case of estrogen alone. It seemed to be attributable to the inhibitory effect of the progesterone on the motility of the uterus. 5. There was a remarkable discrepancy between the fluctuation of the impulse(integral) of the uterine pressure and that of the frequency of the contraction. Apparently inverse relationship was noticed, suggesting that more powerful contraction was brought by less frequent uterine contraction.