Metachromatic leukodystrophy is due to deficiennt activity of arylsulfatse A, an enzyme important in myelin catabolism. The deficiency can be caused by different point mutations in the gene coding for arylsulfatase A (nonfunctional alleles). In addition, certain mutations result in low levels of enzyme activity detectable with artificial substrates in vitro but no clinical dysfunction (pseudodeficiency alleles). The described family has various combinations of normal, nonfunctional, and pseudodeficiency alleles that presented diagnostic and counseling dilemmas which were resolved at the genomic levle. We find no evidence that compound beterozygote individuals have subclinical involvement of the nervous system. We report the clinical, pathological, electrophysiological, imaging, biochemical, and genetic data of this family and discuss the difficulties in analyzing such pedigrees.