Introduction: PSP is a rare degenerative disorder associated with significant morbidity. Recently, investigations of the etiology and treatment of PSP have been initiated. The aim of the present study was to validate the motor domain of the Progressive Supranuclear Palsy Rating Scale (PSPRS) as part of a larger epidemiological study. Methods: Fifty videos of patients with PSP were rated by four trained movement disorder neurologists using the PSPRS. Reliability and construct validity of the scale were evaluated using standard methods. Results: Inter-rater reliability for the total scale score was good. Internal consistency of the scale improved with the removal of three items. Four factors accounted for the majority of the variance of the scale as determined by principal components analysis. Discussion: This study shows that the motor domain of the PSPRS is a reliable scale, with a factor structure that suggests construct validity, for the assessment of motor signs of the disease. Removal or modification of items may improve the clinimetric features of the motor domain of the scale.