Aim II. To develop an objective, composite iTUG mobility score. We recently demonstrated that iTUG metrics are more sensitive in distinguishing mobility performance between people just diagnosed with PD from age-matched controls than traditional clinical tests. In this proposal, we will develop a composite mobility score from the iTUG gait and postural parameters most responsive to severity of PD and to the change from the levodopa ON and OFF states. The composite score will be calculated using statistical models that optimize differences in performance between 75 subjects with PD in the ON and OFF levodopa state.