The number of state-funded prekindergarten programs continues to grow in the United States. The quality of these early childhood programs, however, often depends on the type of professional development provided. In this investigative study, an experimental pre-post causal-comparative research design was employed to evaluate the impact of an 8-week curriculum course on state-funded prekindergarten teachers' knowledge about developmentally appropriate curriculum, their beliefs about best practice, and their actual observed classroom instructional performance. The 8-week course focused on equipping teachers of 4-year-olds with the content knowledge and instructional strategies necessary to promote children's learning. Based on research about the critical role of interactions on learning, the nature and types of exchanges between teachers and children became the focus of the professional-development initiative. Nine teachers attended the course and were evaluated before and after the training. A control group of 8 teachers was also assessed during the same time frame. An analysis of the data revealed that the course was effective in changing prekindergarten teachers' knowledge and practice. Results from pre-post measures of beliefs demonstrate that the outcomes were less significant. The impact of this focused professional-development initiative was not mediated by the participating teachers' level of education. (Contains 8 tables.)