Brain-derived neurotrophic factor (BDNF) is widely expressed in the mammalian brain. BDNF has been shown to promote differentiation and survival of all major neuronal types affected in Parkinson's disease (PD). PD is a neurodegenerative disorder of the central nervous system characterized pathologically by the loss of dopaminergic neurons in the substantia nigra pars compacta. Cerebrospinal fluid (CSF) contains factors that are important to the survival of dopaminergic neurons. In this study CSF BDNF concentrations were measured in patients with PD and in normal controls. A total of 48 CSF samples from patients with PD (n=24) and controls (n=24) were studied. We used Western blot analysis and enzyme-linked immunosorbent assay to study BDNF expression and concentration. The amount of BDNF was clearly increased in CSF samples from patients with PD when compared with normal CSF. BDNF could be involved in the pathophysiology of PD.