A variety of deletional and point mutations has been identified in the parkin gene on chromosome 6q25.2-27 in patients with autosomal recessive juvenile parkinsonism, a distinct form of familial Parkinson's disease (PD). To study the potential involvement of the parkin gene in development of non-hereditary idiopathic PD, a codon 167 serine/asparagine (167S/N) polymorphism located in its exon 4 was analyzed by direct sequencing in 71 patients with sporadic PD and 109 age-matched non-PD controls. The frequency of either 167S or 167N allele was not statistically different between PD patients and controls, while the frequency of 167S/N heterozygotes was significantly higher in PD patients (62.0% vs 45.9%), compared with that of both 167S/S and 167N/N homozygotes combined (chi2 4.467, p = 0.0346; odds ratio = 1.92, 95% confidence interval = 1.05-3.54). These observations suggest that the heterozygosity at codon 167 in the parkin gene might represent a genetic risk factor for development of sporadic PD.