Adrenoleukodystrophy (ALD) is an X-linked disorder that involves mainly the nervous system white matter and adrenal cortex. It is associated with the accumulation of saturated very-long-chain fatty acids (VLCFAs), such as hexacosanoic acid (C26:0), that occurs as a result of the impaired capacity to degrade these substances, a reaction that normally takes place in the peroxisome. The VLCFAs originate from the diet and are also synthesized endogenously. Interest in dietary therapy arose from the observation that the administration of oils containing erucic and oleic acid (Lorenzo's oil), when combined with restriction of dietary intake of VLCFAs, can normalize plasma VLCFA levels in ALD patients. Clinical results in patients who are already symptomatic have been disappointing. However, preliminary data, still in need of confirmation, suggest that dietary therapy begun in asymptomatic patients can reduce the frequency and severity of later neurological disability.