To study the effect of sex hormone and ATP, one of the most important high energy phosphate in the body metabolism, on the uterine weight/body weight, and glycogen of the endometrium of the castrated albino rat, the authors performed following experiment. The results obtained were as follows: 1) Three weeks after castration, estrogen 100γ+ATP 1mg per day for three days were injected in mature female rat. In estrogen+ATP group the uterine weight, uterine weight/body weight were increased significantly and the glycogen were increased in the stroma and gland of the endometrium of the uterus than estrogen alone group. 2) Three days after castration of mature female rat, estrogen 10γand ATPγmg per day were injected for three days. In estrogen+ATP group uterine wight, uterine weight/body weight, and glycogen of the endometrium were increased than estrogen alone group. 3) In Progesterone and ATP group, there were no significant changes than progesterone alone group. And in testosterone and ATP group there were same findings. 4) In immature female rat three weeks after castration, estrogen 25γ and ATP 250γ per day for three days were injected. There were no significant changes in uterine weight, uterine weight, body weight, and glycogen of the endometrium than estrogen alone group(25γ per day for three days).