Oral chronic GVHD (cGVHD) is a serious complication of alloSCT. Scales and instruments to measure oral cGVHD activity and severity have not been prospectively validated. The objective of this study was to describe the characteristics of oral cGVHD and determine the measures most sensitive to change. Patients enrolled in the cGVHD Consortium with oral involvement were included. Clinicians scored oral changes according to the National Institutes of Health (NIH) criteria, and patients completed symptom and quality-of-life measures at each visit. Both rated change on an eight-point scale. Of the 458 participants, 72% (n=331) had objective oral involvement at enrollment. Lichenoid change was the most common feature (n=293; 89%). At visits where oral change could be assessed, 50% of clinicians and 56% of patients reported improvement, with worsening reported in 4-5% for both the groups (weighted kappa=0.41). Multivariable regression modeling suggested that the measurement changes most predictive of perceived change by clinicians and patients were erythema and lichenoid, NIH severity and symptom scores. Oral cGVHD is common and associated with a range of signs and symptoms. Measurement of erythema and lichenoid changes and symptoms may adequately capture the activity of oral cGVHD in clinical trials but require prospective validation.