The melanocortin receptor 1 (MC1R) plays a central role in regulation ofeumelanin (black/brown) and phaeomelanin (red/yellow) synthesis within themammalian melanocyte and is encoded by the classical Extension (E) coat colorlocus. Sequence analysis of MC1R from seven porcine breeds revealed a total offour allelic variants corresponding to five different E alleles. The Europeanwild boar possessed a unique MC1R allele that we believe is required for theexpression of a wild-type coat color. Two different MC1R alleles were associatedwith the dominant black color in pigs. MC1R*2 was found in European Large Blackand Chinese Meishan pigs and exhibited two missense mutations compared with thewild-type sequence. Comparative data strongly suggest that one of these, L99P,may form a constitutively active receptor. MC1R*3 was associated with the blackcolor in the Hampshire breed and involved a single missense mutation D121N. Thissame MC1R variant was also associated with EP, which results in black spots on awhite or red background. Two different missense mutations were identified inrecessive red (e/e) animals. One of these, A240T, occurs at a highly conservedposition, making it a strong candidate for disruption of receptor function.