Three male siblings in a gypsy family presented with congenital Addison's disease. The youngest showed neurological signs at the age of ten and deteriorated rapidly. The eldest had convulsive symptoms and the third an irregular E.E.G. Investigation of the youngest by means of cerebral biopsy revealed rarefaction of myelin with perivascular sudanophil deposits. An ultrastructural study showed frequent liposfuscin deposits in the astrocytes and oligodendrocytes. In the peripheral nerve there were signs of re-myelinization associated with hypertrophy of Schwann cells. These various aspects have led to these cases of demyelinization associated with adrenal deficiency being classified among the leukodystrophies while some authors have interpreted these lesions as characteristic of Schilder's disease. The fact that in thirty or so cases published, almost half of which are familial, only boys are affected supports the theory of an enzymopathy at the root of both leukodystrophy and adrenal atrophy.