Guiding Inservice Mathematics Teachers in Developing a Technology Pedagogical Knowledge (TPCK) Margaret Niess, KwangHo Lee, Pejmon Sadri, Gogot Suharwoto Department of Science and Mathematics Education Oregon State University Corvallis, OR 97331 USA niessm@onid.orst.edu , leekw@onid.orst.edu , sadrip@onid.orst.edu , suharwog@onid.orst.edu Abstract: Few teachers have used spreadsheets as tools for learning mathematics, leaving many of them unprepared to guide students in learning mathematics with spreadsheets. Current teachers have not had any preparation that develops technology pedagogical content knowledge (TPCK) - the intersection of the knowledge of mathematics with the knowledge of technology (spreadsheets) and with the knowledge of teaching and learning. This professional development program focused on guiding teachers in developing TPCK for teaching mathematics with spreadsheets. Actual teaching opportunities were extended by classroom observations and support as teachers implemented their developing ideas. Research results revealed potential key attributes of a TPCK professional development program along with a preliminary model for describing the developmental progress of the inservice teachers in their growth in TPCK. Spreadsheets offer a technology readily available among classroom technologies to support students in learning mathematics. However, its use is limited or even nonexistent in most mathematics classrooms largely because mathematics teachers have not been prepared to use spreadsheets in thinking about mathematics, nor have they been prepared to integrate spreadsheet technology as a tool for teaching and learning mathematics. If spreadsheets are to be included as tools for learning mathematics, then mathematics teachers need opportunities to develop their personal knowledge and skills of using spreadsheets as tools for exploring and learning mathematics. They need support in redesigning the mathematics curriculum to include spreadsheets as tools for exploring mathematics while also guiding their students’ development of knowledge and basic skills with spreadsheets. They need support in guiding student thinking of mathematics with spreadsheet tools. Inservice teachers need a preparation that they likely have not experienced as they learned mathematics nor as they learned to teach mathematics. And, as inservice teachers who are actively engaged in teaching, they have limited time for extensive educational programs that require such a significant shift in what and how they teach. When and how will they gain these new skills for teaching mathematics in the 21 st century? What type of professional development will meet the teachers’ needs in ways