In this investigation we employed a case study approach with qualitative and quantitative data sources to examine and discover the characteristics of the processes used by a midwestern U.S. school system to adopt and implement a new K–6 science curriculum. Analysis of data yielded several results. Elementary teachers received what they requested, a hands-on science program with texts and kits. Teachers as a group remained in the early stages of the Concerns-Based Adoption Model profile of concerns. Many K–6 teachers remained uncomfortable with teaching science. Teachers' attitudes regarding the new program were positive, and they taught more science. Teachers struggled with science-as-inquiry, with a science program they believe contained too many concepts and too much vocabulary, and with their beliefs that students learned more and loved the new hands-on program. Traditional science teaching remained the norm. Administrative support was positive but insufficient to facilitate full implementation of the new program and more substantial change in teaching. Standardized science achievement test scores did not show an observable pattern of growth. It is concluded that a systematic, ongoing program of professional development is necessary to address teachers' concerns and help the district realize its goal of standards-based K–6 science instruction. © 2004 Wiley Periodicals, Inc. J Res Sci Teach 42: 25–52, 2005