Development of a suitable measure of quality of movement, or gross motor performance, for children with cerebral palsy is a complex undertaking. A variety of conceptual, methodological, and practical issues inherent in such a project are discussed in this article. We report on the methodology used in the planning and construction of the Gross Motor Performance Measure. The measure has been developed by a multicenter, interdisciplinary group of therapists, methodologists, research staff, and international experts. Five attributes of gross motor performance have been defined, scaled, and operationalized. Results of content validity studies demonstrate that the measure has adequate completeness, clarity, and potential for evaluating change in quality of movement in children who have cerebral palsy. The measure is currently undergoing extensive testing to determine the reliability, validity, and responsiveness of the obtained scores. [Boyce WF, Gowland C, Hardy S, et al. Development of a quality-of-movement measure for children with cerebral palsy.