While it is generally accepted that pedagogical content knowledge (PCK) is an essential knowledge base for science teachers, educational researchers are not clear on how it develops. Previous researchers have suggested that classroom practice may play a significant role. Therefore, it is important to look at beginning teachers' PCK and its development during the first years in the classroom. Using the pilot year data from a larger study, we developed and employed a rubric to help understand 24 beginning secondary science teachers ‘PCK, focusing on two categories: Knowledge of Student Learning and Knowledge of Instructional Strategies. The results of analysis did not show a statistically significant change between the groups, but when comparisons were made with all of the teachers, the category of Knowledge of Students Learning did significantly change. In this paper we report the results of the pilot year data, provide examples of how we employed the rubric to assess teachers’ PCK, and discuss how this study benefits understanding beginning teachers' PCK.