Adrenoleukodystrophy was diagnosed pathologically in 17 male patients. The diagnosis was suggested by clinical and laboratory signs of primary adrenal failure and by neurological signs referable to the degeneration of white matter. Neurological findings usually predominated over clinical stigmata of adrenal failure. Adrenal biopsy has proved to be the most reliable diagnostic test, while brain biopsy has often been misleading. The histological picture of the brain lesion differs substantially from that of the adrenal, but the presence of similar ultrastructural cytoplasmic inclusions suggests a common metabolic disorder. Morphological analysis of the cerebral lesion indicates that the destruction may spread in a caudal-rostral direction. The intense inflammatory cell response occurs within the demyelinated areas, behing the area of active myelin breakdown, and appears to be a secondary feature of white matter degeneration.