Background: There is no documented demographical study on Iranian Parkinson's disease (PD) patients, so this study was conducted to identify demographic information about patients with PD in Iran, and to explore demographical differences between PD patients in Iran and other countries.Methods:We reviewed medical records of 1656 patients diagnosed with PD, who referred from all parts of Iran to a referral Parkinson's disease clinic in Tehran. We collected data about their age, gender, age of onset, side of motor symptoms' onset, and drug history.Results:This study was performed on 1656 patients with idiopathic Parkinson's disease, and the results showed that, out of 1656 cases, 1132 patients were males (68.4%) and 524 patients were females (31.6%). The mean age of these patients was 65.16 ±11.9 years (16-99 years). The mean age of onset in these patients was 53.16 ±12.5 years (12-90 years). Among 697 patients, 345 patients (49.5%) had right onset PD, and the remaining 352 cases had left onset PD (50.5%). Side of motor symptoms onset was not associated with the age of the patients at disease onset (P > 0.05). The incidence of right onset PD in males was 50.1% and 48.2% in females, although this difference was not statistically significant (P > 0.05). There was no significant difference between males and females in age of onset (P > 0.05).Conclusion:Our data suggests that the male to female ratio among Iranian Parkinson's disease patients is much higher than other countries. Additional investigation is required in this field.