The third volume of the proceedings of 21st annual meeting of the International Group for the Psychology of Mathematics Education contains the following papers: (1) "Graphics Calculators Use in Precalculus and Achievement in Calculus" (P. Gomez and F. Femandez); (2) "Tapping into Algebraic Variables through the Graphic Calculator" (A. Graham and M. Thomas); (3) "Collaborative Mathematical Reasoning in an Inquiry Classroom" (B. Graves and V. Zack); (4) "Working from the Inside with Theory from the Outside" (U. Hanley and T. Hardy); (5) "Gender Difference and Their Relation To Mathematics Classroom Context" (M. Hannula and M.-L. Malmivuori); (6) "Are Lawyers-Prey To Probability Misconceptions Irrespective of Mathematical Education?" (A. Hawkins and P. Hawkins); (7) "An Expression of the Idea of Successive Refinement in Dynamic Geometry Environments" (O. Hazzan and E. P. Goldenberg); (8) "Effectiveness of a Strategy as a Sociomathematical Norm" (P.G. Herbst); (9) "How Equally Suited is Realistic Mathematics Education for Boys and Girls? A First Exploration" (M. van der Heuvel-Panhuizen); (10) "Teacher as Amplifier, Teacher as Editor: A Metaphor Based on Some Dynamics in Communication" (D. Hewitt); (11) "Using the Computer To Improve Conceptual Thinking in Integration" (Y.Y. Hong and M. Thomas); (12) "Investigating Children's Collaborative Discourse and Verbal Interaction in Solving Mathematical Problems" (H.-M.E. Huang); (13) "An Analysis of Student Talk in 'Re-learning' Algebra: From Individual Cognition To Social Practice" (B. Hudson, S. Elliott, and S. Johnson); (14) "The Cognitive and Symbolic Analysis of the Generalization Process: The Comparison of Algebraic Signs with Geometric Figures" (H. Iwasaki and T. Yamaguchi); (15) "Making Sense of Mathematical Meaning-Making: The Poetic Function of Language" (M. James, P. Kent and R. Noss); (16) "Children Learning To Specify Geometrical Relationships using a Dynamic Geometry Package" (K. Jones); (17) "Change in Mathematics Education: Rethinking Systemic Practice" (L.L. Khisty); (18) "Area Integration Rules for Grades 4, 6 and 8 Students" (G. Kidman and T.J. Cooper); (19) "Teachers' Pedagogical Content Knowledge of Multiplication and Division of Rational Numbers" (R. Klein and D. Tirosh); (20) "Gender Differences in Algebraic Problem Solving: The Role of Affective Factors" (S. Kota and M. Thomas); (21)"Students' Representations of Fractions in a Regular Elementary School Mathematics Classroom" (M. Koyama); (22) "Number Instantations as Mediators in Solving Word Problems" (B. Kutscher and L. Linchevski); (23) "The Mathematical Knowledge and Skills of Cypriot Pupils Entering Primary School" (L. Kyriakides); (24) "Some Issues in using Mayberry's Test To Identify van Hiele Levels" (C. Lawrie and J. Pegg); (25) "Defining and Understanding Symmetry" (R. Leikin, A. Berman and O. Zaslavsky); (26) "The Psychology of Mathematics Teachers' Learning: In Search of Theory" (S. Lerman); (27) "On the Difficulties Met by Pupils in Learning Direct Plane Isometries" (N.A. Malara and R. Iaserosa); (28) "The Dialectic Relationships between Judgmental Situations of Visual Estimation and Proportional Reasoning" (Z. Markovits and R. Hershkowitz); (29) "An Analysis of the Teacher's Role in Guiding the Evolution of Sociomathematical Norms" (K. McClain and P. Cobb); (30) "Negotiation of Meanings in the Mathematics Classroom" (L. Meira); (31) "The Use of the Graphing Calculator in Solving Problems on Functions" (V.M. Mesa); (32) "A Hierarchy of Students' Formulation of an Explanation" (I.A.C. Mok); (33) "The Role of Writing To Foster Pupils' Learning about Area" (C.O. Moreira and M. do Rosario Contente); (34) "Learning Process for the Concept of Area of Planar Regions in 12-13 Year Olds" (C. Comiti and B.P. Moreira); (35) "Study of the Constructive Approach in Mathematics Education: Types of Constructive Interactions and Requirements for the Realization of Effective Interactions" (T. Nakahara); (36) "Real Word Knowledge and Mathematical Knowledge" (P. Nesher and S. Hershkovitz); (37) "Immediate and Sequential Experience of Numbers" (D. Neuman); (34) "Microanalysis of the Ways of using Simpler Problems in Mathematical Problem Solving" (K. Nunokawa); (35) "Pupils' Perception of Pattern in Relation To Shape" (J. Orton); (36) "Early Representations of Tiling Areas" (K. Owens and L. Outthred); and (37) "What Can be Done To Overcome the Multiplicative Reversal Error?" (D. Pawley and M. Cooper). (ASK)