This secondary analysis study focused on how interactions among preservice teachers' pedagogical content knowledge (PCK) components developed throughout a 14-week CoRe-based mentoringenriched practicum course, and the nature of those interactions. Data were collected from three preservice teachers, information-rich cases, by the use of content representation (CoRe) and semi-structured interviews. Content analysis and the constant comparative method were employed in the data analysis. Results revealed that the development of integrations was idiosyncratic. Additionally, PCK integration moved from fragmented to a more integrated and coherent one by the end of the semester. Implications for science teacher education and research are discussed. (C) 2014 Elsevier Ltd. All rights reserved.