as part of a summer professional development institute, we investigated how a focus on the explanatory power of different proofs helped in-service teachers enhance their understanding of mathematical proof. i will present example problems and several solutions in order to illustrate different types of proof and what we mean by explanatory power. in addition, i will discuss the different types of teaching practices that the instructor of the institute used in order to facilitate changes in participants' understanding of proof. this talk is intended for undergrads, grads, and professors.