This is a report of a case of the adult cerebral form of X-linked ALD. The 27-year-old patient presented with psychiatric disturbances. NMR was performed and compared to CT scan to define cerebral demyelination. The level of hexacosanoate was found to be increased in the patient's serum. Biochemical analysis of the patient's mother's serum and cultured fibroblasts and of serum samples from 10 other members of the family who could have been carriers of this X-linked disease, produced negative results. Hence, it is most likely that this case has occurred sporadically. HLA determination revealed the DR2 antigen which is often associated with multiple sclerosis.