Epidermal melanocytes, derived from neural crest cells, are mainly responsible for melanin in skin. In human skin, nearly all normal pigmentation is due to melanin and with the exception of hemoglobin, it is one of the only endogenously synthesized pigments in man. Melanin has numerous functions in mammals, including increasing the optical efficiency of the eye, producing color patterns in various organs, including hair or skin, serving as camouflage, heat exchange, sexual recognition and protection from sunlight,z. The incidences of malignant melanoma have been increasing dramatically in western countries, at least by a factor of 15 over the past 60 years, and this has caused an intense interest in understanding melanogenesis3-5. More than 40,000 new cases of malignant melanoma have been diagnosed in 19976, and it is one of the most common cancers in young adults. The research in the area of melanogenesis has exploded during the last ten years because model systems to study molecular mechanisms regulating melanogenesis have become available. This review examines currently available in vitro and in vivo model systems to study melanogenesis.