Scale construction is a growth enterprise in the psychological literature. Unfortunately, many measures promise much but are severely limited by the inadequacies of their conceptualization and execution. In this paper, a model for developing psychological scales is presented that is rooted in the traditions of construct validity and classical test theory but informed by modern psychometric methods. Construct validity is conceptualized as a guiding principle in each of three phases of scale development, focused on (i) construct conceptualization and development of the initial item pool, (ii) item selection and structural validity, and (iii) assessment of external validity vis-à-vis other measures and relevant nontest criteria.