Disorders of pigmentation were among the first genetic diseases ever recognized because of their visually striking clinical phenotypes, resulting from defects of pigmentary melanocytes. Recent years have seen remarkable progress in understanding these diseases, largely as a result of the systematic parallel study of human patients and inbred mice with similar phenotypes. Our understanding of disorders of pigmentation indicates that these diseases may be most usefully considered as abnormalities of melanocyte development, function, or survival.