Abcd1 knockout mice, a model for the adrenomyeloneuropathy (AMN) form of X-linked adrenoleukodystrophy (X-ALD), cannot transport a subset of substrates over the peroxisomal membrane, presumably saturated and/or unsaturated very long chain fatty acid CoA esters. This evidence concerns the gene ABCD1 and X-linked adrenoleukodystrophy.