Questioning is an essential and generative studying practice for prospective teachers (PTs) as they develop their mathematical content knowledge needed for teaching. This study examines PTs' questioning interactions by describing the types of questions they ask during small group discussions in a required mathematics content course and how their questions contribute to the mathematical argumentations produced in these small group discussions. This study employs a case study approach, integrating data from participant-observation (in particular the transcription data generated from audio/video recordings of these observations), participant-generated written documents (e.g., PTs' course notebooks), and interviews to create pictures of the mathematical questioning practices of the three focus PTs. The questions asked by the three focus PTs in small group discussions were examined to develop an inductively generated classification scheme of questioning interactions. Results from the classification scheme illustrated that there were two common questioning themes for all three PTs' questioning practices. The first common questioning theme was questioning to support the sharing of group members' ideas. The second theme was questioning to support the validation for the focus PTs' ideas. In order to describe how PTs' questioning interactions contribute to mathematical argumentation, this study uses Toulmin's scheme of argumentation to produce argumentation maps illustrating how and when PTs use questions during argumentation. Results from the argumentation analysis illustrated that the focus PTs and their group members did not typically ask questions soliciting backing for warrants. Further, when discussions were conceptual in nature, it was often the instructors who prompted backing through questioning. Overall, very few of the focus PTs' questioning interactions were successful in contributing to the sociomathematical norm of what counts as an acceptable argumentation by eliciting conceptual discourse. The PTs' questions analyzed in this study illustrate that the focus PTs did not ask many questions soliciting conceptual discourse. Questioning to solicit conceptual discourse prepares PTs in ways that are specific to their work as future teachers. Thus, what we learn from these three cases is that PTs need opportunities and support in order to promote this types of questioning during teacher education courses. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]