In coming to better value teachers' knowledge and practice, there is a need to be able to articulate and document what teachers know and are able to do. This is central in coming to understand pedagogical content knowledge (PCK). This paper presents a working understanding of PCK as it has emerged through a research project and describes the development of a method of documenting PCK, the Pedagogical and Professional-experience repertoire (PaP-eR). (Contains 14 references.) (WRM)