Origins of Mathematical Abilities. What a Number Is: Mathematical Foundations and Developing Number Concepts (K.F. Miller). Relationships Children Construct Among English Number Words, Multiunit Base-Ten Blocks, and Written Multidigit Addition (K.C. Fuson, J.L. Fraivillig, B.H. Burghardt). Understanding Elementary Mathematics (J. Bisanz, J.-A. LeFevre). Mathematical Misunderstandings: Qualitative Reasoning About Quantitative Problems (R.E. Mayer, A. Bovenmyer Lewis, M. Hegarty). The Role of Expertise in Solving Arithmetic and Algebra Word Problems by Analogy (L.R. Novick). The Development of Skill in Mental Arithmetic: An Individual Differences Perspective (K.F. Widaman, T.D. Little). Numerical Cognition: Representation, Process, and Architecture. A Theory of Enumeration that Grows Out of a General Theory of Vision: Subitizing, Counting, and FINSTs (L.M. Trick). Working Memory, Automaticity, and Problem Difficulty (M.H. Ashcraft et al.). Representation and Retrieval of Arithmetic Facts: A Network-Interference Model and Simulation (J.I.D. Campbell, M. Oliphant). MATHNET: Preliminary Results from a Distributed Model of Arithmetic Fact Retrieval (M. McCloskey, A.M. Lindemann). Inhibitory Mechanisms in Normal and Dysfunctional Number Processing (J.M. Clark). Cognitive Number Processing: An Encoding-Complex Perspective (J.I.D. Campbell, J.M. Clark). The Functional Architecture of Numerical Processing Mechanisms: Defending the Modular Model (M. McCloskey, P. Macaruso, T. Whetstone). In Defense of the Encoding-complex Approach: Reply to McCloskey, Macaruso, & Whetstone (J.I.D. Campbell). Author Index. Subject Index.