Description: Teaching is described here in the context of knowledge transformations, from expert framework ? teaching framework ? student understanding. Changes in these knowledge frameworks are illustrated by qualitative differences in concept map structures. Methodology: The use of PowerPoint presentations in teaching helps to make explicit the teaching structure that is being projected in the classroom and provides an arena for reflection. Examination of PowerPoint presentations reveals a tendency to amplify a linear knowledge structure that is often promoted by common teaching practices. For students who are actively engaged in their learning, such a linear structure may provide an impediment to the construction of expertise which is not typically linear in structure. Expert knowledge is represented by concept maps that are highly integrated network structures. Conclusions: Recognition of this problem can help teachers to reflect upon their PowerPoint presentations and accompanying handouts and make modifications that are more likely to support the development of expert knowledge in their students. This process will improve the affordances for active learning that may be provided by PowerPoint-supported lectures.Examples are given from a number of academic disciplines.