ccording to the current state of research, it seems uncontroversial that the Pedagogical Content Knowledge (PCK) of teachers is a crucial factor for the success of teaching and learning in the context of many school subjects. Yet, the research about PCK in the subject of computer science (CS) is still sparse. Thus, we are working on a conceptualization of PCK for computer science (CS) that is based on literature on the one hand and empirically validated on the other. As a first step towards this goal, we have developed a category system from a set of publications from general pedagogy as well as from educational research in other subjects. Additionally, we have compared this system with the outcomes of a former survey among teachers about the preparation of lessons. Currently, we are coding all curricula for teacher education in Germany with this category system and preparing interviews among experts, applying the Critical Incident Technique.