The purpose of this study was to investigate the potential contribution of genetic variants in the estrogen receptor beta gene to the aetiology of Parkinson's disease (PD). Several lines of evidence from human and animal studies suggest a protective role for estrogen in PD. Recently the estrogen receptor beta subtype was reported to be an important mediator of estrogen actions in the nigrostriatal dopamine system. Two single nucleotide polymorphisms at position 1730 and 1082 in the ER beta gene were genotyped, using pyrosequencing, in 260 patients with PD and 308 controls recruited from the Swedish population. Neither of the two estrogen receptor beta polymorphisms was associated with an increased risk for PD. However, the G allele of the A1730G polymorphism was more frequent in patients with an early age of onset than in patients with a late age of onset of PD (P = 0.006). Patients carrying the GG genotype had an odds ratio of 2.2 for having an early onset of PD compared to non-carriers. In conclusion, our results indicate that genetic variation in the estrogen receptor beta gene may influence the age of onset of PD.