X-linked adrenoleukodystrophy (X-ALD) is a puzzling inborn error of metabolism with a strikingly heterogeneous clinical spectrum. All patients have mutations in the ABCD1 gene and accumulate very long chain fatty acids in all tissues. Virtually all male X-ALD patients develop adrenocortical insufficiency in childhood and progressive myelopathy and peripheral neuropathy in adulthood. A subset of male patients, however, develops a fatal cerebral demyelinating disease, cerebral adrenoleukodystrophy. Female patients also develop progressive myelopathy and peripheral neuropathy, but generally at a later age than males. They only very rarely develop adrenocortical insufficiency or cerebral adrenoleukodystrophy. This review proposes to simplify the classification of the clinical spectrum of X-ALD and reviews the largely unresolved pathophysiological mechanisms and the current treatment options.