This conference proceedings contains three plenary session reports, 12 working group and 79 research reports, 35 short oral reports, 60 poster session reports, and two discussion group reports. Major papers (excluding "short orals" and "posters") include: (1) "Semantical Obstacles in Mathematics Understanding" (Carlos Arteaga and Manuel Santos); (2) "Mathematical Beliefs and Conceptions of College Algebra Students" (Victor V. Cifarelli and Tracy Goodson-Espy); (3) "Mathematical Intimacy: Local Affect in Powerful Problem Solvers" (Valerie A. DeBellis); (4) "A Modeling Approach to Non-Routine Problem Situations" (Helen M. Doerr); (5) "Posing Questions or Reformulation of Problems as an Activity to Perceive the Structure of Mathematical Problems" (Juan Estrada); (6) "An Analysis of Mathematics Problems in Middle School Textbooks" (Yeping Li); (7) "Recognizing Isomorphism and Building Proof: Revisiting Earlier Ideas" (Ethel M. Muter and Carolyn A. Maher); (8) "Students' Strategies for Searching the Instantaneous Flow in a Graphical Representation of Time versus Volume" (Rodolfo Oliveros); (9) "An Investigation of the Ability to Process and Comprehend Text on Student Success in Solving Algebraic Word Problems" (David K. Pugalee); (10) "Variables Influencing the Effectiveness of Small-Group Work: A Year Long Study of Collaborative Math Problem Solving in Two Fourth-Grade Classrooms" (Rose Sinicrope, Marion A. Eppler, Marsha Ironsmith); (11) "Creating the Conditions for Conceptual Change" (Judy Clark and Joan D. Lukas); (12) "Assessing Students' Attitudes toward Mathematics from a Multilevel Perspective" (George Frempong); (13) "Studying the Impact of Reformed Mathematics Curricula" (Mary C. Shafer and Norman Web); (14) "Connecting Students' Everyday Mathematics and School Mathematics" (Marta Civil, Melanie Ayers, Jose David Fonseca, and Leslie Kahn); (15) "A Vygotskian Action-Research Model for Developing and Assessing Conceptual Models and Instructional Materials Inter-Actively" (Karen C. Fuson, Bruce Sherin, and Steven T. Smith); (16) "Relating Equity to Classrooms Which Promote Understanding: Identifying Relevant Issues" (Lynn Liao Hodge); (17) "The Power of One in a Mathematics Classroom: Lisa and Divisibility by Four" (Kathy M.C. Ivey); (18) "Students' Use of Function Ideas in Everyday Activities" (Joanna O. Masingila and Helen M. Doer); (19) "Mathematics Power: Developing the Potential to Do Work" (Rodney E. McNair); (20) "Using the Metaphor of Voice to Investigate the Mathematical Experiences of African American Students" (Vivian R. Moody and Patricia S. Moyer); (21) "The Impact of a Secondary Preservice Teacher's Beliefs about Mathematics on Her Teaching Practice" (Babette M. Benken and Melvin (Skip) Wilson); (22) "Implementing Mathematics Reform: A Look at Four Veteran Mathematics Teachers" (M. Lynn Breyfogle and Laura R. Van Zoest); (23) "Reflections about Listening and Dialogue as Evidence of Teacher Change" (George W. Bright, Anita H. Bowman, and Nancy N. Vacc); (24) "Shifting Beliefs: Preservice Teachers' Reflections on Assessing Students' Mathematical Ideas" (Patricia S. Moyer and Vivian R. Moody); (25)"Understanding How Prospective Secondary Teachers Avoid Accommodating Their Existing Belief Systems" (Daniel Siebert, Joanne Lobato, and Stacy Brown); (26) "Self-Estimating Teachers' Views on Mathematics Teaching--Modifying Dionne's Approach" (Gunter Torner); (27) "Learning to Teach Mathematics Using Manipulatives: A Study of Preservice Elementary School Teachers" (Sunday A. Ajose); (28) "Prospective Elementary Teachers' Constructions of Understanding about Multiplication with Rational Numbers" (Diane S. Azim); (29) "Narrative as a Tool for Facilitating Preservice Mathematics Teacher Development" (Olive Chapman); (30) "Teacher Change during an Urban Systemic Initiative" (Thomas G. Edwards and Sally K. Roberts); (31) "Cases as Contexts for Teacher Learning" (Megan L. Franke, Elham Kazemi, Jeffrey Shih, and Stephanie Biagetti); (32) "Preservice Elementary Teachers Learning to Integrate Mathematics with Other Subjects through Interdisciplinary Instruction" (Susan L. Hillman); (33) "Using Conceptual Design Tools to Foster Learning in the Game Design Environment" (Yasmin B. Kafai, Megan L. Franke, Jeffrey C. Shih, and Cynthia C. Ching); (34) "Redefining 'The Object' of Assessment in Clinical Interviewing" (Rochelle G. Kaplan and Peter M. Appelbaum); (35) "Professional Development and Systemic Reform: Some Important Connections" (Andrea Lachance and Jere Confrey); (36) "An Analysis of Two Novice K-8 Teachers Using a Model of Teaching-In-Context" (Cheryl A. Lubinski, Albert D. Otto, Beverly A. Rich, and Patricia A. Jaberg); (37) "Preservice Teachers' Ideas about Teaching Mathematics: Contributions to Frameworks for Teacher Education Courses" (E.E. Oldham, A.E. van der Valk, H.G.B. Broekman, and S.B. Berenson); (38) "Classroom Teachers Becoming Teacher Educators: 'Just' Facilitators or Active Agents?" (Deborah Schifter and Susan Jo Russell); (39) "Using Thought-Revealing Activities to Stimulate New Instructional Models for Teachers" (Roberta Y. Schorr and Richard Lesh); (40) "The Role of Formal and Informal Support Networks as Teachers Attempt to Change Their Practice from Traditional to Innovative Reform-Oriented Teaching of Mathematics" (David Feikes); (41) "Enhancing the Pedagogy of University Faculty through Mentoring and Reflection: Preliminary Observations" (Lynn C. Hart); (42) "Developing Teachers' Ability to Identify Student Conceptions during Instruction" (Miriam G. Sherin); (43) "Characterizing a Perspective on Mathematics Learning of Teachers in Transition" (Martin A. Simon, Ron Tzur, Karen Heinz, Margaret Kinzel, and Margaret Schwan Smith); (44) "Investigating Teachers' Insights into the Mathematics of Change" (Janet S. Bowers and Helen M. Doerr); (45) "Technology, Students' Understanding of Graphs, and Classroom Interactions" (Maria L. Fernandez); (46) "Learning the Standard Addition Algorithm in a Child-Centered Classroom" (Betsy McNeal and Betty Tilley); (47) "Megan: 'Seventeen Take Away Sixteen? That's Hard!'" (Catherine A. Pearn); (48) "Thinking in Units: An Alternative to Counting as a Basis for Constructing Number" (Grayson H. Wheatley and Anne M. Reynolds). (ASK)