Several lines of evidence indicate that immune mechanisms are involved in the pathogenesis of neurodegenerative disorders. Activated immunocompetent cells and inflammatory cytokines are present in affected brain regions in patients with Alzheimer's (AD) and Parkinson's disease (PD). For AD biochemical and pathological data are supported by genetic studies identifying risk alleles for polymorphisms in regulatory regions of the interleukin-1 alpha (IL-1 alpha-889) and interleukin-1 beta (IL-1 beta-511) gene, respectively. The partially overlapping pathology and inflammatory reaction pattern between AD and PD led us to investigate these polymorphisms in a large sample of 295 German PD patients and 270 healthy controls. We found T in position -511 in the IL-1 beta gene more frequent in patients compared to controls (chi(2)=4.44, P=0.034). For the IL-1 alpha-889 polymorphism no significant difference between patients and controls was observed.