This chapter outlines some key teacher professional development (TPD) programmes that have attempted to address the issue of teacher domination of classroom talk, observed particularly in the UK and USA. In most classrooms, teachers almost invariably guide and control the discourse, holding interpretive authority while students participate passively and with limited epistemic agency. The chapter identifies which features of dialogue appear to be more often adopted by teachers and students and then consider the key factors contributing to why dialogue is not commonly observed in primary/elementary or secondary schools. The goals and outcomes of most TPD interventions seem to converge on increased sharing and elaboration of different ideas by students rather than critical evaluation, known to promote learning as students test their ideas against others’. Some important design and methodological features of TPD programmes themselves may further help to explain why traditional practices are often resistant to intervention and why clear-cut results are rarely obtained.