Two brothers are described in whom adrenoleukodystrophy (ALD) presented as progressive cerebral degeneration in early adult life. Diagnosis during the life of one brother was based on cerebral biopsy appearances. At autopsy there was a leucodystrophy and an additional myelopathy in both cases. Biochemical studies carried out on the propositi and other family members revealed characteristic abnormalities of ALD in the propositi and two, as yet clinically unaffected, adult brothers, and abnormalities characteristic of the heterozygous state in their mother. Neither of the clinically affected brothers showed clinical features of hypoadrenalism and these cases emphasize the importance of considering the diagnosis of ALD in adult males with leucodystrophy even in the absence of overt adrenal insufficiency.