Introduction/Rationale: A diet that consists predominantly of long-chain monounsaturated fatty acids has been demonstrated to reduce the levels of very long chain fatty acids (VLCA) in individuals with X-linked adrenoleukodystrophy (ALD). VLCFA are the primary biochemical abnormality in this genetic disorder and have been implicated in the pathogenesis of the cerebral disease. It has been demonstrated in an open study that reduction of VLCFA for more than a year is protective for childhood cerebral disease.