Mentor-novice collaborative reflection about teaching is crucial to the development of novices' professional knowledge. However, few studies examine content and forms of mentor-novice conversations and opportunities that such interactions create for developing professional knowledge. Drawing on observation data from two U.S. and two Chinese mentor-novice pairs in induction contexts, this study analyzed the content and forms of mentor-novice conversations about novices' lessons. We found that the U.S. and Chinese mentor-novice interactions were different in focus and form, and these differences were likely related to the curriculum structures and organization of teaching and mentoring in each country. The interactions either offered or restricted novices' opportunities for developing professional knowledge necessary for reform-minded teaching.