The purpose of this study was to assess the effectiveness of a Local Systemic Change (LSC) initiative (N ¼ 216) at Year 2 in a 5-year plan. Key questions were: What is the extent of school and teacher involvement?; What is the impact on teacher preparedness, attitudes, and beliefs?; and What is the extent of institutionalization? The model of professional development used shared leadership (Lead Teachers & Study Groups) along with workshops in inquiry, content, and assessment. All teachers averaged 81 hours of participation by the end of Year 2; LTs averaged 161 hours. Longitudinal and episodic data were collected using multiple instruments, including Horizon Research Teacher Survey (Baseline and Year 2), SG and Lead Teacher surveys (Year 1 and Year 2), Context Beliefs About Teaching Science and Classroom Observation Protocol (Year 2). Gains in teachers' practices, beliefs, and professional culture (collegiality and department chair support) were measured at significance levels of .05. The results indicate that sustained and intensive professional development influences individuals and school culture. ß 2004 Wiley Periodicals, Inc. J Res Sci Teach 42: 3-24, 2005Successful models of professional development in science education generally rely on evidence of change in individual teacher's knowledge, beliefs, and practices. The literature base has documented that high-quality, intensive, and sustained workshops, seminars, and courses promote reform-oriented growth in beliefs, pedagogical content knowledge, and disciplinary content knowledge among teachers. As important as these changes have been in refining the research community's understanding of the multiple dimensions of effective teaching and learning, it is time to move forward into the next generation of professional development, where the focus of change is extended to the teacher and to the teacher's professional community.