Metachromatic leukodystrophy is a genetical disorder due to a deficiency of arylsulphatase A activity. According to the age of onset of symptoms three different forms of the disease are described: late infantile, juvenile and adult types. We report the clinical, neuroimaging, biochemical and morphological features in a man in which the first symptoms ensued at the age of 39. In this patient, whose clinical manifestations were represented by "psychiatric" symptoms, the onset was particularly late in comparison with the large majority of the previously reported cases.