Biopsies from 74 cases of vitiligo were examined to study the reactions of marginal melanocytes. In 35 cases, the melanocytes at the edge of the patch appeared highly dendritic and large with marked arborisation of the dendrites between the surrounding epidermal cells. These cells showed low pigmentation but a high enzyme activity which extended along the dendrites. The enzymes include tyrosinase/dopa oxidase, dopamine oxidase and noradrenaline activity, indicating that these cells have a biphasic melanogenic/adrenergic differentiation.This similarity between the dendritic melanocytes and the amelanotic melanoma cell line HT-18 is of interest.