The purpose of this study was to examine the effects of professional development (PD) on the infusion of engineering design into high school curricula. Four inservice teachers with backgrounds in physics, chemistry, industrial education, math, and electrical engineering participated in the 2006 National Center of Engineering and Technology Education (NCETE)-sponsored PD workshops at California State University, Los Angeles (CSULA) and provided three sources of data that were used to answer the research question, "What are the effects of PD on infusing engineering design into high school science, technology, engineering, and math (STEM) curricula"? Three major themes emerged from the data. They were (a) incorporation of PD content, (b) challenges with incorporating PD content, and (c) benefits of incorporating PD content. It was shown that the effect that the NCETE PD had on the infusion of engineering design into high school curricula varied among each of the four teachers due to their subject area, educational backgrounds, and experiential knowledge. Implications of these findings may be used to inform the design and delivery of future STEM PD efforts. [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.]