The study sample will include 100 Israeli Jewish patients with early idiopathic PD who were not treated with anti-parkinson drugs. The clinical diagnosis will be based on the criteria of the United Kingdom Parkinson Disease Society Brain Bank.5 All patients will undergo Tc-99m-Trodat1 SPECT. The severity of the motor symptoms will be assessed with the Unified PD Rating Scale (UPDRS). Genomic DNA is extracted from peripheral blood leukocytes for genetic analysis.