A family with adrenoleucodystrophy linked to chromosome X (X-ALD) is reported. Three patients, one man (proband) and two female monozygotic twins, had adrenomyeloneuropathy (AMN) which is a form of the disease. The proband had characteristic changes in MRI with demyelination of the white matter in the cerebral hemispheres. Both women (one of them was proband's mother) has somewhat less severe AMN form, but in her twin sister the syndrome was much more intense. The clinical diagnosis of the disease was confirmed by biochemical investigations--determination of the level of very long chain fatty acids, ALDP protein and the activity of peroxysomal beta-oxidation.