As the number of PDS programs increased and awareness of the time, energy, and resources required became more evident, calls for evidence of PDS impact increased. Since 1998, researchers have attempted to design studies that investigate PDS structural features and participant outcomes more systematically. They have used both qualitative and quantitative methods in efforts to learn from and preserve the complexity and nuance of PDSs while determining the importance and strength of particular features. This article focuses on the impact of PDS preparation on teacher candidates based on systematic research, both qualitative and quantitative, published in peer-reviewed journals. It describes the types of studies conducted, the sources of data used, and the teacher candidate outcomes investigated. The results are summarized and linked to salient PDS structural and organizational factors. (Contains 2 tables.)