The importance of using dialogue as a pedagogical tool to enhance student learning in science has been widely recognised in research literature. Effective classroom dialogue is dependent upon teaching which successfully engages students in critical thinking and deep learning, requiring many teachers to think and work differently in science education. To understand the implications of such pedagogy for teaching practice, it is vital to determine how teachers presently consider and enact the role of dialogue in their science teaching. The study discussed in this paper examines how four primary teachers think about and use dialogue to develop scientific thinking and understanding in their primary classrooms. The study was conducted with teachers working in an inner city, primary school in Melbourne, Australia. Data sets included in-depth, semi-structured interviews conducted with the participant teachers, along with three classroom observation sessions recorded with small groups in each participant teacher's classroom. A talk analysis framework, informed by existing literature, was developed and applied to the classroom observation data. Key findings emerged which identified the teacher as critical to the development of effective dialogue, determining the degree of time provided for dialogue, the nature of the interactions taking place and the questioning used to both promote student reasoning and also challenge student thinking. The analysis also raises considerations about appropriate expectations of higher level thinking in any given dialogue and supports a position which sees worthwhile value for students in building teacher knowledge and capacity to enact effective dialogue in science.