This PME-NA proceedings volume contains the full text of 41 research papers. In addition, brief usually one-page reports, are provided for 11 oral presentations and 13 poster sessions. The full research reports are as follows: "Cognitive Analysis of Chinese Students' Mathematical Problem Solving" (J. Cai and E. A. Silver); (2) "Mathematical and Verbal Abilities in Mathematical Problem Solving by Talented Students" (S. D. Moore); (3) "One Student's Effort in Resolving His Self-Generated Measurement Problem: 'See If It Would Work With a Triangle.'" (A. Reynolds and G. H. Wheatley); (4) "Problem Solving Using Arithmetic and Algebraic Thinking" (A. R. Teppo and W. W. Esty); (5) "The Development of Children's Concept of Unit--Grades 4-8" (S. J. Lamon); (6) "Interaction and Fraction Knowledge: Children's Construction of the Iterative Partitioning Scheme" (R. Tzur); (7) "Using Case Studies to Promote Instructional Change" (B. Armstrong, And Others); (8) "The Validity of Concept Maps as a Research Tool in Remedial College Mathematics" (J. Laturno); (9) "Collaborative Action Research in Mathematics Education" (A. M. Raymond); (10) "Middle School Students' Perceptions of Their Everyday Mathematics Usage" (J. O. Masingila); (11) "A Basis for Equity in Mathematics Education: An Experiment In Cultural Course Development" (N. C. Presmeg); (12) "A Case of Equity Reform In Mathematics" (B. F. Risacher); (13) "The Negotiation of Social Norms in a Mathematics Class" (S. D. Trowell and G. H. Wheatley); (14) "Exploring the Social in Social Construction" (S. R. Williams and K. M. C. Ivey); (15) "Empowering Students to Talk About Mathematics In a Seventh-Grade Classroom" (V. M. Adams); (16) "Confidence in Answer Keys Among College Calculus Students" (H. T. Barton); (17) "Enhancing Student Interest in Mathematics Using Integrative Curricula" (M. Mitchell); (18) "The Effects of Psychosocial Variables on Middle School Student Problem-Solving Achievement in Mathematics" (J. L. Nath, And Others); (19) "Justifying the Reasonableness of Answers: Processes of Middle School Mathematics Students" (S. E. Williams and J. V. Copley); (20) "A Teacher's Perception of Time in a Mathematics Classroom" (K. M. C. Ivey); (21) "Preservice Secondary Teachers' Beliefs About Mathematics and Their Expectations About Student Performance on Open-Ended Assessment Tasks" (B. W. Grover and P. A. Kenney); (22) "Changing the Mathematics Learning Environment in Relation to Beliefs, Knowledge, and Practices" (P. A. Jaberg and C. A. Lubinski); (23) "Connecting Orientation Towards Authority to First-Year Teachers' Thinking About Teaching" (B. E. Shealy); (24) "Transforming Mathematics Teaching in Grades K-8: The Role of Material Resources in Supporting Teacher Change" (L. R. Davenport); (25) "Affective Issues in Developing Mathematics Teaching Practice" (L. T. Goldsmith and L. R. Davenport); (26) "Case Studies on Empowering Secondary Mathematics Teachers in Computer-Intensive Environments" (M. K. Heid, And Others); (27) "Perceived Deficits in Middle Grades Mathematics Teaching" (M. K. Heid, and S. J. Feeley); (28) "How Middle School Teachers Adjust to Change: Classroom Testing Of Materials From An Innovative Curriculum Project" (D. V. Lambdin and R. V. Preston); (29) "The Needs of Second Career, Secondary Mathematics Teachers: How Well Are They Met by Academic Programs and Inductive Processes?" (S. A. Maxwell); (30) "Development of Classroom Social Norms and Mathematical Practices with Preservice Teachers" (B. McNeal and M. A. Simon); (31) "Teaching in an Era of Reform: Mathematics in Elementary Classrooms" (P. Sztajn and F. K. Lester, Jr.); (32) "Changing Practice: Describing Mathematics Teachers' Development Through A Modification of Perry's Scheme" (M. R. Wilson and M. P. Goldenberg); (33) "Teacher's Graphical Representations of Rate of Change" (S. B. Berenson and G. S. Carter); (34) "Distributive Flaws: Latent Conceptual Gaps in Preservice Teachers' Understanding of the Property Relating Multiplication to Addition" (S. Campbell and R. Zazkis); (35) "Elementary Teachers' Understanding and Implementation of Unitizing Operations" (T. L. Golding and M. J. Behr); (36) "Elementary School Teachers' Perceptions of Algebra: The Role of Modelling and Technology" (B. J. Pence); (37) "Learning Mathematics While Teaching" (S. J. Russell, And Others); (38) "Teacher's Changing Conceptions of the Nature Of Mathematics" (D. Schifter); (39) "The Fundamental Theorem of Arithmetic: Used and Confused" (R. Zazkis and S. Campbell); (40) "Delineating the Transformation of Subject-Matter Knowledge in Pedagogical Content Knowledge" (C. L. Ebert); and (41) "Pedagogical Content Knowledge, Curricular Knowledge and Teacher Change" (B. S. Rich, And Others). (WTB)