Questionnaire-based measures of function have been validated extensively in studies of chronic illness and work-related low back pain. These measures have only recently been developed for upper extremity disorders (UEDs), and there is little information on their utility in evaluation of injured workers. We developed the Upper Extremity Function Scale (UEFS), an eight-item, self-administered questionnaire, to measure the impacts of UEDs on function. This instrument was tested in a cohort of 108 patients with work-related UEDs and 165 patients with the carpal tunnel syndrome (CTS); both groups were enrolled in prospective follow-up studies. The UEFS demonstrated excellent psychometric properties, including good internal consistency (Cronbach's alpha > 0.83), relative absence of floor effects, and excellent convergent and discriminant validity, compared with measures of symptom severity and clinical findings. In the CTS group, the UEFS was more responsive to significant improvements over time than clinical measures such as grip and pinch strength. These data support the use of a self-reported functional scale as a measure of outcome in studies of work-related UEDs. Further investigations in working populations are needed to substantiate its utility in workers with UEDs who have not yet sought medical care.