Recent work on the melanocortin 1 receptor (MC1R) suggests that MC1R plays a central role in regulation of eumelanin (brown/black melanins) and phaeomelanin (red/yellow melanins) synthesis within the mammalian melanocyte. In the mouse,genetic studies show that the MC1R appears to be a unique, bifunctionally controlled receptor, activated by alpha-MSH and antagonized by agouti,both of which contribute to the variability seen in mammalian coat color. Variants of this receptor are associated with different animal's coat,human skin and hair colors. In addition, cutaneous pigmentation is a major determinant of the cutaneous response to ultraviolet radiation,and consequently of the risk of developing skin cancer. MC1R variants are a risk factor for melanoma susceptibility.