Seven alleles of the chicken melanocortin (MC) 1 receptor were cloned into expression vectors, expressed in mam-malian cells and pharmacologicallycharacterized. Four of the clones e +R ,e +B&D ,e wh /e y ,E Rfayoumi gave receptors to which melanocortin stimulating hormone (a-MSH) and NDP-MSH bound with similar IC50values and responded toa-MSHbyincreasing intracellular cAMP levels in a dose-dependent manner.