RELIABLE AND VALID MEASURES OF RELEVANT constructs are critical in the developing field of the empirical study of research ethics. The early phases of scale development for such constructs can be complex. We describe the methodological challenges of construct definition and operationalization and how we addressed them in our study to develop a measure of perception of voluntariness. We also briefly present our conceptual approach to the construct of voluntariness, which we defined as the perception of control over decision making. Our multifaceted approach to scale development ensured that we would develop a construct definition of sufficient breadth and depth, that our new measure of voluntariness would be applicable across disciplines, and that there was a clear link between our construct definition and items. The strategies discussed here can be adapted by other researchers who are considering a scale development study related to the empirical study of ethics.