AbstractCytosolic and nuclear progesterone receptor levels (RPCRPN) were measured in normal and in pathological human endometria after single-dose progesterone injection 1-3 h before tissue collection (test subjects) and the results compared to those obtained in controls (no progesterone treatment). In test cases of late proliferative or midcycle normal endometria and in estrogen-primed normal postmenopausal endometria, RPNlevels were higher and RPClevels were lower compared with those obtained in control samples. In test cases of postmenopausal pathological endometria, histologically normal endometria of women with postmenopausal bleeding and in one case of endometrial polyp, RPNlevels were also higher and RPClevels lower than those in the respective controls, but the change of distribution of the RP (cytosol/nuclear extract) was significantly lower than in normal endometrium.