White female rats from the Wistar strain were divided into three groups: the first--subjected to heavy motion exercises, the second--used as control, and the third--immobilized. Motion stress was accomplished by use of a tretbahn, while immobilization was effected by the use of a method for physiological immobilization invented by the authors. A considerable reduction in corpus luteum number (number of ovulations) was observed in the immobilized animals. In most cases cystic degeneration, ovarian hypoplasia, obliteration and obturation as well as salpingitis were observed in these animals also. In pregnant immobilized rats only a small number of embryos was found, high percent of embryo mortality, fetal growth retardation and a considerable thickening and folding of the endometrium with numerous blood cells mainly histocytes and lymphocytes under the epithelium. No visible deviations from the normal condition and function of the gonads were observed in the control animals while in those under motion stress data indicating a certain improvement in the reproductive activity were obtained.