An increased frequency of the A-allele of the alpha-antichymotrypsin (ACT) gene has been recently described in Japanese patients suffering from Parkinson disease (PD). In the present study, we have analyzed 62 German PD patients with regard to their ACT and APOE genotypes and compared them to 53 controls without clinical or pathological evidence of neurodegenerative disease. The A-allele frequency was 47% in PD patients compared to 54% in control cases excluding ACT as a major susceptibility factor for PD in the Caucasian population. Yet, ACT-A allele frequencies were significantly different (p < 0.001) between Japanese and German controls. Therefore, although our data do not suggest that the alpha1-ACT polymorphism is a significant risk factor for the development of PD, a consideration of differences in genetic background seems warranted when evaluating susceptibility factors for neurodegenerative disease.