The authors studied the topographic distribution and the hormonal regulation of glycogen and lipids in the uterus of adult spayed rabbits treated with oestradiol and progesterone following histochemical and biochemical methods. The glycogen is localised, on the one hand, in the muscular cells of the arteriolar circumference and in the perivascular conjunctival sheaths of the endometrium, and, on the other hand, in the myometrium, where it is specially found in the interior, circular, muscular layer. This deposition of glycogen is provoked by oestradiol but is inhibited by progesterone. The uterus of spayed rabbits untreated or treated with progesterone contain only traces of glycogen and this only at the myometric level. The lipids, which are absent in the uterus of spayed animals, make their apparition in the fibroblastic cells of the chorion just underlying the endometrial epithelium under the action of oestradiol. They disappear when progesterone is given along with oestradiol. Whereas when progesterone is given after a previous treatment by oestradiol, it produces small deposits of lipids in the basal part of the epithelial cells of the »uterine lace«. When progesterone alone is given, it produces no effect. The hepatic accumulation of glycogen and the fasted blood sugar are not affected by our doses of oestradiol and progesterone. There was no apparent parallelism observed between the hepatic glycogenopoiesis and the uterine glycogenopoiesis. The uterine growth in spayed rabbits after an administration of progesterone (0.33 mg/kg. day for 6 consecutive days), without a previous activation by oestradiol, is discussed and is attributed to a direct effect of the progesterone on the uterus. * Aspirant du Fonds National de Belge de la Recherche Scientifique. Adresse actuelle: Harvard Medical School, Department of Medicine, and Peter Bent Brigham Hospital, Boston 15, Mass., U. S. A.