The design of this study was a multiple case study conducted to examine the knowledge, pedagogical principles, and challenges involved in providing engineering-oriented professional development for teachers at the secondary school level. A set of criteria was used to identify five representative projects for analysis in the US. A variety of tools and processes were used to gather data including on-site observations, interviews, focus groups and document reviews. Results of the study indicate that engineering professional development tends to be based on work focused on curriculum development and implementation. Given the distinct design orientation of engineering, it is not surprising that the focus of engineering-oriented professional development tends to concentrate on engaging activities, with a primary focus on process rather than content. A key outcome of this study was an observed lack of a clearly formulated and articulated conceptual foundation for secondary level engineering. Regarding pedagogy, the researchers identified a heavy emphasis on modeling and applied learning. At the same time, the researchers observed a lack of emphasis on reflection and analysis of the pedagogical processes and techniques used to shape teachers' ability to teach engineering to their students. The findings of the study also include concerns raised by teachers as they engage in engineering professional development. These include concerns about technical knowledge, particularly with the use of specialized software applications and other tools, as well as with practical issues such as time, resources, and availability of appropriate curriculum.