This study serves to collate and evaluate measures of self-directed learning (SDL), with the goal of guiding the measurement and discussion of SDL. Used in a variety of settings, many applications of SDL have been proposed, but a consistent definition has yet to be formulated. Despite the lack of a cohesive definition, several tools exist to measure SDL. Within this study, which implemented the preferred reporting items for systematic reviews and meta-analyses (PRISMA) and Consensus-Based Standards for the Selection of Health Status Measurement Instruments (COSMIN) protocols, 157 articles were analyzed for content and themes were identified. An important finding of this study was a definite lack of cohesion in application and understanding of SDL as a framework. While some regard it as a stand-alone learning intervention, others address it as a personality trait. Close examination of the instruments used to measure SDL led to the conclusion that it is both inappropriate and ineffective to continue using, as they broadly lack construct validity and generalizability. Limitations of this study are single subject research, number studies available within databases used, and lack of raw data from studies covered. Future research surrounding the conceptual framework and instrumentation is indicated to further develop the field's understanding of SDL's value and implications. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]