This paper reports an analysis of qualitatively different ways in which teachers experience change in their understanding of subject matter they have recently taught. In this exploratory study, interviews with 31 'typical' teachers from a range of first and second-year university subjects revealed that 20 reported no experience of change in their understanding. The reports of the 11 teachers who did experience change were used in a phenomenographic study from which five qualitatively different categories of description of change were constituted. These range from the experience of change as the adding of unproblematic knowledge to what is already known, to questioning the theoretical framework of the subject matter. The relation between the experience of change in understanding and the experience of teaching and learning for the 31 teachers was also explored. It was found that the teachers who did not experience change in their understanding were more likely to experience teaching as the transmission of knowledge, and the teachers who experienced change in their understanding, and who experienced that change as the re-interpretation or questioning of knowledge, were more likely to experience teaching as changing or developing students' conceptions.