OBJECTIVES: Skin scars impact quality of life (QoL), quantification of which is essential to evaluate the effectiveness of treatment. As no suitable instruments were available the objective of the study was to develop and validate the first patient-reported scale of scar-specific symptoms and QoL. METHODS: Questionnaire content was derived from qualitative interviews with UK scar patients. Face and content validity were assessed by cognitive debriefing interviews conducted with patients. The final instrument was determined using Rasch analysis and psychometrically assessed in a validation survey. RESULTS: Five hundred and sixty-seven potential items were extracted from 34 qualitative interview transcripts. Following review and reduction, 16 symptom and 36 QoL items were identified. The draft scales were found to be relevant, clear and easy to use in 16 patient interviews. Two QoL items were deleted as patients considered them too extreme. Following the validation survey (n=103), 10 QoL and 3 symptom items were removed: eight misfit the Rasch model (Chi2 p>0.05); four were redundant and one functioned differently according to age. Rasch analysis confirmed two unidimensional scales (p<0.05). Internal consistency was good for both the symptoms and QoL scales (0.84 and 0.85) as was test-retest reliability (0.83 and 0.89 respectively). The symptom scale was shown to be statistically significantly related (as expected) to scores on the Hospital Anxiety and Depression Scale (HADS) and the clinician-completed Manchester Scar Score (MSS). The QoL scale was also statistically significantly related to scores on these measures and on patient-reported scar severity. CONCLUSIONS: PRISM is the first scientifically rigorous patient-reported instrument designed specifically for scar patients. It consists of two unidimensional scales with good psychometric and scaling properties: QoL (24 items) and symptoms (13 items). PRISM is well accepted by patients, easy to use and should prove valuable for assessing scar disease severity in clinical trials and practice.