A mid-Atlantic state has recently adopted the Next Generation Science Standards (NGSS) that require teachers to integrate inquiry-based instruction into the classroom. The problem at the local level is a new inquiry-based curriculum, based on the NGSS, is being mandated without identifying the instructional strategies teachers are using to implement the new standards. The purpose of this project study was to explore fourth- and fifth-grade science teachers' inquiry-based instructional strategies, why the strategies were chosen, and teachers' concerns about the implementation of the strategies. In this case study, the concern-based adoption model and self-efficacy were used as a conceptual framework to capture the experiences and perceptions of the participants' implementation of inquiry-based instruction. Data were collected, in the form of interviews, lesson plans, and classroom observations, from nine fourth- and fifth-grade elementary teachers in a rural, mid-Atlantic school system setting. The participants were interviewed about their implementation of inquiry-based instruction and classroom observations and documents were gathered to provide corroborating evidence. Open-coding strategies were used to analyze the data. The findings from this study supported the need for increased professional development for elementary teachers to implement inquiry-based lessons. Consequently, a professional development plan was developed to help address teachers' concerns by providing information on the implementation of a new inquiry-based curriculum, based on NGSS, and give voice to elementary science teachers. The results influence positive social change by supporting teachers' implementation of practices that support students' learning in science. [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://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]