The purpose of this study was to determine the qualitative and quantitative distribution of melanocytes in human leptomeninges by histochemical and ultrastructural techniques and to search for melanocytes in the mesothelial linings of the pleural and peritoneal cavities. Knowledge of the extracutaneous distribution of pigment cells will facilitate the interpretation of systemic symptoms in depigmentation disorders, such as vitiligo and the Vogt-Koyanagi-Harada syndrome. In 15 brains examined, leptomeningeal pigment cells were found principally over the ventrolateral surfaces of the medulla oblongata. Only isolated pigment-containing cells were found in the meninges covering other parts of the brain. The mean number of pigment cells in the medullary meninges of 5 brains was 325/mm2 +/- 96. The presence of melanosomes as single, membrane-bound granules in all stages of melanization confirms that the melanin-containing dendritic cells of the leptomeninges are melanocytes and not macrophages. No pigmented cells were observed in the pleural or peritoneal samples examined.