This article is informed by the findings from a recent research project that investigated how expertise in the teaching and learning of mathematics in early childhood could be enhanced. It involved five teachers from three West Auckland kindergartens. The teachers implemented one action-research cycle (Cardno, 2003; McNiff & Whitehead, 2005) to examine their practices with a view to making change in response to areas they self-identified for development. The teachers used a range of data-gathering methods to collect qualitative evidence of mathematics teaching and learning. These included reflective journals, learning stories, parent voice, note keeping, photographs, and small-scale surveys. This article discusses ideas unearthed through the research process: * Teachers' subject knowledge in mathematics is essential for effective mathematics teaching and learning. * Teachers' confident dispositions towards mathematics is fundamental for their engagement in mathematical teaching and learning. * (Pedagogical) documentation enhances the teaching and learning of mathematics in early childhood. * Visibility of children's work through documentation is an integral method for sharing children's mathematical thinking with parents and whanau, and the community. An important characteristic of this research project was that the reflective nature of the action-research process (identification of the research problem, implementation of new ideas, and evaluation of the progress), which acted as a useful learning tool for the teachers by provoking them to consider the teaching and learning of mathematics in their specific contexts. In all three kindergartens, teachers used their participation in the project to focus on how they could share children's mathematics learning with a range of stakeholders, in particular, the children themselves and the kindergarten community. One teacher surmised: We want to use this opportunity to work more closely with our [parents and whanau] and to share with them what maths their children are doing while at kindergarten. Early on in the project, data led the teachers to identify a variety of perceived barriers to enhancing children's mathematical experiences. After some analysis of this data, it was evident to the teachers that they needed to increase their documentation of children's mathematical thinking. This led them to the realisation that fundamental to effective documenting of learning and teaching episodes that demonstrated children's mathematical thinking was the issue of their own mathematical confidence, and this in turn was related to their own personal subject knowledge of mathematics (Anning & Edwards, 1999). The teachers recognised that these two attributes, subject knowledge and confidence, would enable them to enrich young children's mathematical experiences and provide strategies for sharing these with the children and their parents and wha nau. The teachers reflected: We've got to take a long hard look at ourselves, what we do and what we provide, before we move forward. If we agree that we can't be effective mathematics teachers in this culture, then it's a problem we can't change. That means we can't be a better maths teacher because of the barriers. I think we need to improve ourselves to get over these barriers. Hence, the research project unfolded in two directions: first, it explored how an increase in teachers' subject knowledge, and increased confidence, might affect their responses to children's mathematical thinking; and second, it explored how teachers supported, challenged, or extended children's mathematical learning. This was aligned with a focus on documenting what learning was noted and recognised as mathematics, together with strategies for sharing this learning with parents and whanau. Teachers' knowledge of mathematics The advantages of personal subject knowledge for early childhood teachers, and in particular in mathematics, are well documented internationally (Anning & Edwards, 1999; Aubrey, 1994; Baroody, 2004; Copple, 2004; Perry & Dockett, 2002). …