Current reform in science education calls for the cohesive integration of scientific and engineering practices, crosscutting concepts, and disciplinary core ideas (National Research Council, 2012; NGSS Lead States, 2013). The purpose of this study is to investigate how practicing middle school science teachers are impacted by their involvement in a comprehensive ? ? professional development program that seeks to adjust their pedagogical content knowledge consistent with current ? ? ? ? reform efforts. During this phase of the overall project, we engaged in a mixed methods investigation including the ? ? ? ? ? ?strategic collection and analyses of both quantitative and qualitative data (Bryman, 2006; Charmaz, 2006; Creswell, 2014; Yin, 2006). Specifically, we respond to the following questions: ?1. How do middle grade science teachers translate into practice the components of a comprehensive professional ?development program? ?2. What factors impact middle grade teachers? enactment of reform efforts in science education? ?Our findings revealed that a combination of science content knowledge and science education courses, and other ? ? ? ? ? ?complementary experiences positively impacted the teaching practices of the middle grade science teachers. Furthermore, immersion into the science practices and principles contained in the reform-based curriculum served as a catalyst for focusing on teaching for conceptual change and meaningful learning of targeted science ideas. However, while the teachers embraced the reform efforts, their perceptions of support from administrators and interpretation of mandates offered constraints. Implications for in-service education for science teachers will be addressed. We therefore submit this proposal to the strand: Transforming Teacher Education at all Levels.