To investigate an involvement of genetic variations of synphilin-1 in development of sporadic PD, a possible single nucleotide polymorphism (SNP) of T131C corresponding to a valine (Val) to alanine (Ala) substitution at codon 44 in exon 3 of the synphilin-1 gene was studied in a Japanese population of 55 patients with sporadic PD and 61 patients with non-PD by direct sequencing analysis.