Background and Context: Pair programming is used in classrooms to promote learning and engage a more diverse group of students in computing fields, but little is known about what it looks like in middle school. Objective: The aim of this study was to examine how programming pairs were interacting and about what. Method: Video, audio, and screen capture data were collected and analyzed from 66 middle school students working in pairs to program a computer game in an after-school class. Findings: Less than half of pairs interaction time was about their game, and one third of their time was spent not interacting at all. Most behaviors were collaborative. There were few differences across demographic groups. Factors that significantly influenced interactions and behaviors included attitude toward collaboration and prior programming knowledge.Implications: We discuss how to use pair programming in the classroom, including how to pair students to promote productive interactions.