|Abstract||This research focuses on inservice science teachers conceptions of nature of science (NOS) before and after a two-week intensive summer professional development program that included explicit NOS instruction. It combines this explicit approach to NOS instruction with reflective, dialogue about the interventions used throughout the professional development. It addresses the seven commonly-held tenets of NOS that are deemed significant to K-12 science teachers. Finally, it borrows qualitative methodologies for analyzing the Views of Nature of Science Questionnaire and associated interviews to gain a richer understanding of the teachers' NOS understanding before and after the interventions. By using this approach to data analysis, this research better describes the ways in which teachers' conceptions of NOS aspects align with and/or deviate from the desired understanding put forth in the professional development. This description of their understanding avoids reducing the participants' diverse and complex conceptions of these tenets into simple "informed" or "naive" categories. It is through this more detailed analysis of the participants' data that this research examines inservice science teachers' conceptions' of nature of science before and after engaging in an explicit, long-term, professional development intervention.