This study was undertaken to determine whether antiserum to the α- and β-subunits of human gonadotropin could affect prolactin secretion from human pituitary cell monolayers. The addition of antiserum to the α-subunit of follicle-stimulating hormone, but not to the α-subunit of luteinizing hormone, at a 1 : 10,000 dilution inhibited basal prolaction secretion. The addition of these antisera failed to inhibit prolactin secretion in the face of 10-5 mol/L gonadotropin-releasing hormone. Coincubation of antiserum to the β-subunit of luteinizing hormone or the β-subunit of follicle-stimulating hormone at a 1 : 10,000 dilution failed to inhibit basal prolactin secretion; however, coincubation of gonadotropin-releasing hormone with antiserum to the β-subunit of either luteinizing hormone or follicle-stimulating hormone significantly inhibited the release of prolactin. These observations led us to conclude that basal and gonadotropin-releasing hormone-mediated prolactin secretion can be affected by gonadotropin subunits. © 1987.