Pedagogical content knowledge (PCK) is the teacher's ability to pedagogically adapt content to students of diverse abilities. In this study, we investigated how teachers' adaptations of instruction for individual students differed when teaching stronger and weaker instructional units. We used functional analysis (Hanley, Iwata, & McCord, 2003) of the instructional interaction to examine PCK. We observed and measured student-teacher interactions and their appropriateness. Participants were 2 experienced elementary physical educators who taught stronger and weaker units. Primarily, the appropriateness data indicated PCK differences between the stronger and weaker units. Results show that functional analysis of instructional adaptations is an effective strategy for examining PCK and that teachers were better able to meet students' needs in the stronger unit. (Contains 2 tables and 2 figures.)