Abstract: An adult case of metachromatic leukodystrophy, proved by characteristic findings of the brain and superficial sural nerve biopsies, without the deficiency of arylsulphatase A activity in the leucocytes, was reported. The significance of long course for thirty years, the absence of deficiency of arylsulphatase A activity, the discrepancy between the normal serologic test and the typical pathological findings in the superficial sural nerve under the light and electron microscopes were discussed as the features of this disorder.