To perform a factor analysis using the University of Washington Quality of Life Questionnaire version 4 (UW-QOLv4) to establish subscales; to report their normative values and variations for patients by age, sex, extent of disease, and time from treatment; and to estimate clinical effect sizes and potential for use in comparative treatment studies. Retrospective cohort. Regional Maxillofacial Unit, University Hospital Aintree, Liverpool, England. Patients with primary oral and oropharyngeal cancer treated by surgery with or without adjuvant radiotherapy since 1992. A database accumulating since 1995 contains more than 2600 UW-QOLs completed by these patients. A data set of 372 patients without cancer attending 10 general dental practices provided normative data. UW-QOLv4. Factor analysis indicated a 2-factor solution: (1) physical function, involving chewing, swallowing, speech, taste, saliva, and appearance, and (2) social-emotional function, involving anxiety, mood, pain, activity, recreation, and shoulder function. The best scores were for those with less advanced oral cancer tumors not requiring free-flap surgery or adjuvant radiotherapy. Older patients reported better scores, but associations were weak, and no sex differences were found. Significant differences were seen for T category, site, free-flap surgery, and adjuvant radiotherapy (P < .001). Preoperative scores were close to normative values. Patients regain social-emotional deficits by 1 year after surgery but continue with significant deficits in physical function. Comparative studies using these UW-QOL subscales as outcome measures should recruit at least 80 patients per treatment arm to detect moderately sized treatment effects. With the UW-QOLv4, it is appropriate to analyze and report outcomes using the 2 subscales of physical and social-emotional function.