Science teacher educators recognise a professional learning continuum for teachers. This has resulted in studies of science teachers at different career stages, with the goal of building an understanding of teacher learning from preparation through practice. While these explorations help build an understanding about teacher learning over time, the work is far from complete. The present study tackles one aspect of teacher knowledge--pedagogical content knowledge (PCK)--from the perspective of the teacher. Specifically, it depicts the PCK of experienced secondary science teachers who are serving as mentors to beginning science teachers. Each teacher ultimately conceptualised PCK as the knowledge for teaching science, and all of the teachers had the following components in their individual models: science, goals, students, curriculum organisation, assessment, teaching, and resources. Each teacher, however, had a personalised representation that directed his or her instructional decisions and actions. While these findings are from a small pool of exceptional teachers, they articulate components that experienced teachers may need to benefit from professional development programmes, along with ways in which these components can interact with practice. A preliminary understanding of the components and their interaction can assist those who plan and implement professional development programmes for science teachers. (Contains 4 tables and 4 figures.)