The presence of the receptor for parathyroid hormone-related peptide (PTHrP) and the effect of PTHrP on adrenocorticotropic hormone (ACTH) secretion in the hen anterior pituitary were examined. The plasma membrane fraction of the anterior pituitary was found to contain a specific chicken PTHrP (cPTHrP) binding component. The binding component had properties of a receptor, such as binding specificity to cPTHrP, reversibility, saturable binding, high affinity, and limited capacity; therefore, it was elucidated that the PTHrP receptor exists in the plasma membrane of the hen anterior pituitary. A third ventricular injection of cPTHrP in nonlaying hens caused a decrease in the chicken ACTH level of the anterior pituitary and an increase in the chicken ACTH level of blood plasma, with an increase in the binding affinity and a decrease in the binding capacity of PTHrP receptor in the anterior pituitary. The present study suggests that PTHrP may act directly on the anterior pituitary via its receptor binding and may enhance ACTH secretion from this tissue in hens.