The authors report on a patient of 33 years of age suffering from neurocutaneous melanosis in whom two years after excision of a naevus pigmentosus et pilosus giganteus cellular proliferation of the melanoblasts in the area of the soft meninges was seen. This process led to the death of the patient within a few weeks' time despite intensive therapeutic measures, the manifestation being that of a generalised space-occupying growth in the CNS. Neuroradiological techniques can objectify the clinical pattern of signs of this very rare disease and may possibly enable an early diagnosis.