The purpose of this study was to develop and validate a new patient-based outcome measure for hand/arm disorders for use in audit, clinical trials and effectiveness studies. There were three stages. First, we carried out interviews with 40 patients with hand/arm disorders to develop and pilot questionnaire content. Second, in a postal survey with 165 pre- and 181 post-surgery patients, we reduced the number of items and identified scales. Third, in a postal survey with 132 pre- and 204 post-surgery patients we evaluated the psychometric properties of the measure. Findings confirmed the acceptability, reliability, validity and responsiveness to clinical change of the questionnaire. The Patient Outcomes of Surgery-Hand/Arm (POS-Hand/Arm) is a new surgical outcome measure that can be used before and after surgery (29 and 33 items, respectively) to evaluate and compare new techniques, surgical teams and units.