This longitudinal case study describes the factors that affect an experienced teacher's attempt to shift her pedagogical practices in order to implement embedded elements of argument into her science classroom. Research data was accumulated over 2 years through video recordings of science classes. The Reformed Teacher Observation Protocol (RTOP) is an instrument designed to quantify changes in classroom environments as related to reform as defined by the National Research Council ("National science education standards". Washington, DC: National Academy Press, 1996b) and the National Research Council ("Fulfilling the promise: Biology education in the nation's schools", Washington, DC: National Academy Press, 1990) and was used to analyze videotaped science lessons. Analysis of the data shows that there was a significant shift in the areas of teacher questioning, and student voice. Several levels of subsequent analysis were completed related to teacher questioning and student voice. The data suggests a relationship between these areas and the implementation of scientific argument. Results indicate that the teacher moved from a traditional, teacher-centered, didactic teaching style to instructional practices that allowed the focus and direction of the lesson to be affected by student voice. This was accomplished by a change in teacher questioning that included a shift from factual recall to more divergent questioning patterns allowing for increased student voice. As student voice increased, students began to investigate ideas, make statements or claims and to support these claims with strong evidence. Finally, students were observed refuting claims in the form of rebuttals. This study informs professional development related to experienced teachers in that it highlights pedagogical issues involved in implementing embedded elements of argument in the elementary classroom.