The lipid composition of tissues from a patient with adrenoleukodystrophy was examined. Cholesterol esters of both brain and adrenal tissues contained increased proportions of fatty acids longer than C22 in agreement with previous reports. During this study, thin-layer chromatographic analysis of the neutral lipid fraction from the cerebral white matter and the adrenal gland revealed an unknown spot, which was identified as hydrocarbon of n-alkanes (CnH2n + 2, n = 16-33) by means of gas-liquid chromatography and gas chromatography/mass spectrometry. There may be a relationship between the accumulation of hydrocarbons and the change in fatty acid metabolism that is the fundamental disorder of ALD, as: (1) the fatty acids abnormally accumulated in cerebral white matter and adrenal gland coincided in chain length (i.e. C24-C26) with the main peaks of n-alkane in the same tissues, and (2) an abnormal accumulation of n-alkanes occurred in the diseased tissues where cholesterol esters with very long chain fatty acids were markedly increased.