Teachers must gauge students' understandings and confusions. Yet most research about teacher thinking neglects teachers' ideas about confusion and students' perspectives about their interactions with their teacher when they are confused. This study examines two high school English teachers' and six of their students' thinking about confusion, addressing two research questions: What sources of information do participants rely on to identify student confusion when students are learning to write about literature? And what do participants' interpretations of that information reveal about their conceptions of confusion, and of teaching and learning? The author used Stimulated Recall Interview method—videotaping two interactive writing lessons and then interviewing each participant about video segments. Analysis involved grounded theory to develop a two-part theoretical framework. Part I examines information sources participants rely on to identify student confusion (including students' unconscious nonverbal cues, intentional signals, written work, and private thoughts). Part II examines four interrelated facets of confusion: the nature of confusion (participants' metaphorical models), types, causes of, and responses to confusion (including who participants felt had agency). Using this framework, the author presents case studies to depict eight participants' unique conceptions of confusion. Two findings emerged: (1) Participants' interpretations of confusion revealed their underlying conceptions of understanding, teaching, and learning; (2) Some students' conceptions of confusion matched their teacher's conception; others mismatched or were in conflict. Implications for teaching practice and student learning are discussed, including the need for teachers to understand how students understand the role confusion plays in learning.