5548 Background: Pt self-reported questionnaires measuring acute and specific effects of OM are needed to assess effects of interventions and guide patient care. We evaluated the feasibility, validity, and reliability of the OMWQ-HN on OM and its impact on pts' abilities to perform alimentary and other routine functions. METHODS Validity and reliability of the OMWQ-HN was assessed in 75 pts from a prospective multicenter study receiving radiotherapy ± chemotherapy (RTCT). Assessments included test-retest reliability, internal consistency reliability, and cross-sectional validity. The OMWQ-HN's sensitivity to detect change was demonstrated by using the changes in the Performance Status Scale for HNC (PSS-HN) and the Functional Assessment of Cancer Therapy (FACT-HN) to form 3 independent groups (better, no change, worse) for comparison. Effect sizes (ES) were calculated for group comparisons to measure the clinical significance of differences. RESULTS Compliance rates were >90% throughout the study. The OMWQ-HN demonstrated good test-retest reliability (r = 0.89). Cronbach's alpha was >0.85 and mouth, throat, and pain-related items correlated highly with each other (r>0.7). Cross-sectional analyses to assess validity showed that OMWQ-HN scores were different across levels of pain, with those in the worst pain category reporting the most severe OMWQ-HN scores (ES >0.5 for all comparisons). The OMWQ-HN was sensitive to change in FACT-HN and PSS-HN (p < 0.001 and p = 0.013, respectively). Patients reported increases in mouth and throat soreness (MTS) that corresponded with a steady decline in oral function. CONCLUSIONS These results indicate the OMWQ-HN is a feasible, valid, and reliable instrument for assessing the impact of mucositis on patients receiving RTCT in the HNC patient care setting. [Table: see text].