Parkinson disease (PD) is a progressive neurologic condition that causes motor and nonmotor manifestations. Treatment provides symptomatic benefit but no current treatment has been proven to slow disease progression. Research studies of PD require a means of rating the severity of disease by measurement of motor manifestations, assessment of ability to perform daily functional activities, and symptomatic response to medication. The most common rating scales are the Unified Parkinson Disease Rating Scale (UPDRS), Hoehn and Yahr staging, and the Schwab and England rating of activities of daily living. Each of these rating scales are described, including detailed instructions on how to implement these ratings. Although these are the most widely applied rating scales of PD, there are still substantial limitations to these scales that must be considered when using them for research. Finally, some common applications of these scales are described.