Adult metachromatic leukodystrophy is a demyelinating disease due to an inherited lack of arylsulfatase A activity. The purpose of this paper is to present the characteristics of this disorder as they occurred chronologically in two siblings, prior to and subsequent to the appearance of gross neurological deficits. A deficit in spatial relationships, as contrasted with verbal abilities, was observed initially in both cases at age 13. Initial psychiatric symptoms were noted at age 16 and 18, with both patients being diagnosed subsequently as schizophrenic. Gross neurological deficits were observed 2 and 13 years, respectively, after the appearance of psychiatric symptoms. A deficit in spatial relationships may be a very sensitive early indicator of adult metachromatic leukodystrophy.