The Proceedings of PME-XVII has been published in three volumes because of the large number of papers presented at the conference. Volume I contains a brief Plenary Panel report, 4 full-scale Plenary Addresses, the brief reports of 10 Working Groups and 4 Discussion Groups, and a total of 23 Research Reports grouped under 4 themes. Volume II contains 37 Research Reports grouped under 7 themes. Volume III contains 28 Research Reports grouped under 5 themes, 25 Oral Communications, and 19 Poster Presentations. In summary, the 3 volumes contain 88 full-scale Research Reports, 4 full-scale Plenary Addresses, and 59 briefer reports. Conference subject matter can be conveyed through a listing of the 15 themes under which Research Reports were grouped: Advanced Mathematical Thinking; Algebraic Thinking; Assessment and Evaluation; Pupil's Beliefs and Teacher's Beliefs; Computers and Calculators; Early Number Learning; Functions and Graphs; Geometrical and Spatial Thinking; Imagery and Visualization; Language and Mathematics; Epistemology, Metacognition, and Social Construction; Probability, Statistics, and Combinatorics; Problem Solving; Methods of Proof; Rational Numbers and Proportions; Social Factors and Cultural Factors. Each volume contains an author index covering all three volumes. (MKR)