In this study, we investigate the role of the C-->G mutation in position 77 of exon 4 of the protein tyrosine phosphatase receptor-type C (PTPRC) gene, coding for the CD45 molecule, for the development of multiple sclerosis (MS) in an Italian continental population. The PTPRC mutated genotype has been recently described as associated with MS in three different case-control studies carried out in German MS patients, whereas similar studies performed in the US and Swedish populations failed to demonstrate such an association. The C-->G transition in position 77 was found in a small number of Italian MS patients and in none of the matched group of healthy controls (Fisher exact test, P value=0.02). This finding suggests a role, in at least a group of patients, for the PTPRC mutation in genetic susceptibility to MS.