SYNOPSIS. Recent advances in the biology of mammalian pigmentation are reviewed.Particular attention is given to emerging information on the integration of pigmentary events occurring at different levels of biological organization within mammalian skin and hair. The structural and functional significance of keratinocytes and melanocytes as components of mammalian epidermal melanin units is viewed from this perspective. New evidence on the nature of genetic, developmental, endocrine, and radiation influences on performance of melanocytes and the establishment of pigmentary patterns is summarized.