In the past few decades there has been an increasing awareness of the importance of early childhood education in New Zealand. Concomitant with this has been the move towards professionalising the early childhood sector through a national curriculum and increased expectations for its practitioners. This paper examines issues relating to the changing role of early childhood teachers as they manage the implementation of the New Zealand curriculum. There is no consensus about what makes up the professional knowledge base for early childhood educators. This paper explores the nature of professional knowledge and suggests that subject matter knowledge may be more important than previously recognised for early childhood educators.