Canavan's disease is an autosomal recessive hereditary leukodystrophy resulting from deficiency of the enzyme aspartoacylase. Two children suffering from this metabolic brain disease were examined using image-guided localized proton spectroscopy. The absolute concentrations of metabolites were determined. These data demonstrate, for the first time, that the well known increase of the N-acetylaspartic acid (NAA)/Cho ratio in this disease may be not only due to a reduction of choline-containing compounds in brain tissue but, at least in specific cases, also due to an increase of the NAA concentration, which is a result of the enzyme defect.