Although the Unified Parkinson's Disease Rating Scale (UPDRS) is widely used to monitor disease progression and drug efficacy, no attempts have been made to evaluate its scientific and clinical quality. Poor clinical sensibility of items in the activities of daily living (ADL) section and redundancy of items in the motor examination (ME) section prompted us to determine if the number of items in these sections could be reduced to a smaller, equally sensitive set that would describe the data as reliably as did the original set of items. Therefore, we assessed 111 patients with idiopathic Parkinson's disease on the UPDRS and Hoehn and Yahr staging scales. Our results show that the ADL (13 items) and ME (14 items) sections can be reduced to 8 items each without loss of reliability or validity. Our report is preliminary and needs validation.