We examine in-service high school teachers' journals to explore the emerging themes in a mathematics content course for their professional development. We use a sociocultural perspective and characterize journals as signifying teachers' communication and written discourses about their thinking and experiences in the course. We use applied thematic analysis to analyze the emerging themes. Our results demonstrate the complexity of teacher thinking and suggest that teachers do not necessarily separate their thinking about themselves or mathematics from their thinking about their students; similarly, they can take different roles as teachers and learners in a given context. Our results indicate exercising caution about potentially operating with an oversimplified picture of teacher thinking via compartmentalized pieces, especially if such frameworks are used to measure teacher thinking, knowledge, and development. [For the complete proceedings, see ED630210.]