Corticotrophin-releasing hormone (CRH) plays a major role in mechanisms controlling human pregnancy and parturition. Gene regulation by progesterone may be a key point in the control of placental CRH production. Studies in primary placental cells show that antagonism of progesterone activity or production by RU486 or trilostane leads to an increase in CRH promoter activity. This effect can be reversed by the addition of progesterone. Overexpression of progesterone receptor A (PR-A) or glucocorticoid receptor resulted in a decrease in CRH promoter activity following progesterone treatment, whereas an increase in promoter activity was observed with overexpressed PR-B. Studies including mutation of the cAMP regulatory element (CRE) confirm this site to be essential for the progesterone-mediated effects. In summary, our results demonstrate that progesterone regulates CRH gene transcription via a CRE in the CRH promoter and that PR-A and PR-B exhibit different actions in the regulation of CRH gene expression.