The aetiology of the selective neurodegeneration in Parkinson's disease (PD) is still unknown. Neurotrophic factors, e.g. glial cell line-derived neurotrophic factor (GDNF), have been shown to promote survival of dopaminergic neurons. Interestingly, aged mice lacking GDNF-receptor (RET) in their dopaminergic neurons show a phenotype similar to presymptomatic PD. We therefore were interested whether polymorphisms in the RET gene were associated with increased PD risk. Analyzing 25 SNPs in the RET region in 340 Southern German PD patients and 340 age- and sex-matched controls from Southern Germany (KORA S4), we did not find any significant association with PD, suggesting that the equilibrium of trophic factors in PD might be disturbed on other levels than the genomic encoding.