Although the melanocyte-stimulating hormone (MSH) is well-recognised as a pigmentary hormone in animals, its role in human pigmentation is still a matter for conjecture, not least because cultured human melanocytes have proved to be relatively refractory to the peptide. However, recent work has shown that human melanocytes can respond to MSH peptides and the related adrenocorticotropic hormone. While the pigmentary responses are the most studied, they are by no means the only effects of these peptides on human melanocytes. This article reviews recent work on the responses of human melanocytes to MSH peptides and demonstrates that these peptides may be key regulators of human melanocyte physiology.