Introduction: Erectile dysfunction (ED) is a disorder in which a male is not able to provide and/or maintain enough erection during sexual intercourse for duration of at least 6 months. Parkinson disease is a neurodegenerative disorder which is clinically identified with motor symptoms, tremor, rigidity and bradikinesia occurring after loss of approximately 70% of dopaminergic neurons in substantia nigra and it gives response to dopamin replacement treatment. Materials and Methods: Severities of Parkinson disease and ED were measured using UPDRS (Unified Parkinson's disease Rating Scale) scoring and IIEF-5 scoring, respectively. The patients were evaluated by Beck's Depression Scale and those patients who were in depression and who had comorbidities (i.e. cerebrovascular diseases, cardiovascular diseases and Diabetes Mellitus) that might causes ED were excluded from study. Thirty (30) patients with Parkinson disease who were 55-78 (mean: 65.26±6.06) years old were included into study. Pearson's test of correlation analysis was used for statistical evaluation. A p<0.05 was regarded to be statistically significant. Results: UPDRS scores and IIEF-5 scores were between 40 and 65 (mean: 50.86±8.93) and between 7 and 17 (mean: 11.06±3.16), respectively. There was no statistically significant correlation between age and IIEF-5 scores (p: 0.17). There was also no statistically significant correlation between age and severity of Parkinson disease (p: 0.19). It was found that there was a statistically significant correlation between severity of Parkinson disease and severity of ED (p<0.0001). Conclusion: ED is an important problem which causes worsening in quality of life in patients with Parkinson disease. Our study confirmed that as severity of disease in patients with Parkinson disease was increased, severity of ED was also increased and quality of life was worsened.