Facial erythema is a primary feature of rosacea. Currently, no validated scales exist that can accurately capture a patient's self-assessment of their own facial erythema. During phase 2 studies for brimonidine tartrate gel, a 5-point numeric rating scale was developed as a tool to allow subjects to provide an independent assessment of visible changes to the facial erythema associated with their rosacea.The objective of this study was to validate the revised patient's self-assessment (PSA) scale and evaluate it for statistical reliability and validity in quantification of facial erythema of rosacea.The validity of the PSA scale was evaluated by assessing the test-retest reliability, construct validity, and known-groups validity based on the data collected during a Phase 2b study on brimonidine gel for the treatment of persistent facial erythema of rosacea.Based on the results of this evaluation, this PSA scale demonstrated test-retest reliability, construct validity, and known-groups validity.Study results are most generalizable to those with moderate to severe erythema.The PSA is an appropriate scale to assess facial erythema associated with rosacea.