Parkinson's disease (PD) is the second most common progressive neurodegenerative disorder characterized by the degeneration of dopaminergic neurons. Detecting changes in gene expression in untreated de novo patients with PD is important for understanding the disease pathogenesis and for identifying biomarkers of the preclinical stage of PD. In this study, the expression of the glycogen synthase kinase-3 beta gene (GSK3B) was investigated in the peripheral blood of several groups of neurological patients using reverse transcription reaction and real-time PCR. Our results suggest that the GSK3B expression level cannot serve as a biomarker for early stages of PD.