A light and electron microscopic study was performed on the cerebral white matter in a case of adrenoleukodystrophy (ALD) with peculiar symptoms of olivopontocerebellar atrophy. The affected white matter on the light microscope had many macrophages containing characteristic membrane-bound linear inclusions. The unaffected white matter on the light microscope demonstrated the following ultrastructural changes: (1) slight but definite degeneration of myelin sheaths scattered among apparently normal myelinated axons; (2) oligodendroglia-like cells containing membrane-free intracytoplasmic inclusions; and (3) many swollen astrocytes containing the same membrane-bound linear inclusions as those in the macrophages within the affected white matter. The mechanism of demyelination in ALD is also discussed.