Objective: Clinical measures that quantify upper extremity function are needed for the accurate evaluation of patients and to plan an intervention strategy. The purpose of this study was to examine the relationship between the Unified Parkinson’s Disease Rating Scale (UPDRS)-Motor Exam and upper extremity performance as a quantifying clinical tool of upper extremity function in persons with Parkinson’s disease. Design: Cross-sectional study. Methods: Thirty-two idiopathic Parkinson’s Disease persons participated in this study. To investigate the relationship between the UPDRS-motor exam, Box and Block test (BBT), and Action Research Arm Test (ARAT) by two physical therapists. The examination took up to 1 hour, and the participants were invited to rest between each clinical measure in order to minimize the effects of fatigue. Clinical measures were assessed while the subjects were in the “on” phase of their medication cycle, generally 1-3 hour after taking their anti-Parkinson’s medications. Results: In more affected side, the UPDRS-motor exam was significantly negative correlated with the BBT (p<0.05) but it was not significantly correlated with the ARAT. In less affected side, only positively correlation was significantly shown between BBT and ARAT (p<0.05). On the other hand, between BBT and ARAT were not significantly correlated with the UPDRS-motor exam. Conclusions: The UPDRS-motor exam is effective tool which was significantly correlated with manual dexterity in more affected upper extremity. But The UPDRS-motor exam is not effective tool in less affected upper extremity.