The identification of immunoreactive β-endorphin, β-lipotropin and ACTH from extracts of human placentas by radioimmunoassay suggests a probable synthesis of these peptides in the placenta. In this study we investigated the presence of β-endorphin and ACTH in placenta, amniotic membranes and umbilical cord using a peroxidase-antiperoxidase staining technique. Tissues were obtained immediately after delivery, fixed in formalin and embedded in paraffin. As control tissues autopsy specimens of pituitary glands from adults and newborns were used. All sections of pituitary glands showed a positive reaction; negative results were observed in sections of placentas, umbilical cords and amniotic membranes. We conclude that no intracellular storage of β-endorphin and ACTH takes place in the examined tissues.