This San Diego State University (SDSU) Noyce Mathematics and Science Master-Teaching Fellowship Program represents a focused and concerted effort to identify effective mathematics and science teachers and provide them with professional development experiences designed to further empower them to improve their practices, serve as mentors for student teachers and novice teachers, and become leaders at their school sites and districts. The program supports the development of Master Teaching Fellows through three research-based phases: (a) the improvement of the Fellows' classroom practices, (b) the development of the Fellows' leadership skills, and (c) the opportunity for the Fellows to continue to grow while they serve as mentors and teacher leaders. The partners are: SDSU College of Sciences, the SDSU College of Education, the nonprofit organization San Diego Science Alliance, three high-needs school districts and a public-private venture with Qualcomm, Inc.'s commitment to support 10 of the 32 Master Teaching Fellows' $10,000 stipends resulting in a corporate-sponsored grant of $500,00 to the project. The Co-PIs support and investigate changes in the Master Teaching Fellows' classroom practices and development as teacher leaders. The project builds on previous work and is designed to support teachers in targeted ways through three research-based phases, recruitment of strong, effective mathematics and science teachers and investigate their changes in classroom practice and in becoming teacher leaders. Long range sustainability is programmed as SDSU's student teachers are to be placed with the Master Teaching Fellows, providing, year after year, opportunities for SDSU's student teachers (long after grant expiration) to receive support consistent with their credential programs.