Teaching Situations as Object of Research: Empirical Studies within Theoretical Perspectives -- Didactical Handling of Students’ Reasoning Processes in Problem Solving Situations -- Macro-Situation and Numerical Knowledge Building: The Role of Pupils’ Didactic Memory in Classroom Interactions -- The Adidactic Interaction with the Procedures of Peers in the Transition from Arithmetic to Algebra: A Milieu for the Emergence of New Questions -- Characterization of an Ordinary Teaching Practice with the Help of the Theory of Didactic Situations -- An Attempt to Model the Teacher’s Action in the Mathematics Class -- Time Management in the Work Economy of a Class, a Case Study: Integration of Cabri in Primary School Mathematics Teaching -- What Can the Teacher Learn in the Classroom? -- Didactic Restrictions on the Teacher’s Practice: The Case of Limits of Functions in Spanish High Schools -- A Cross-Analysis of the Mathematics Teacher’s Activity. An Example in a French 10th-Grade Class -- When Classroom Situation is the Unit of Analysis: The Potential Impact on Research in Mathematics Education -- Analyzing Mathematical Teaching-Learning Situations — the Interplay of Communicational and Epistemological Constraints.New research in mathematics education deals with the complexity of the mathematics’ classroom. The classroom teaching situation constitutes a pertinent unit of analysis for research into the ternary didactic relationship which binds teachers, students and mathematical knowledge. The classroom is considered as a complex didactic system, which offers the researcher an opportunity to gauge the boundaries of the freedom that is left with regard to choices about the knowledge to be taught and the ways of organizing the students’ learning, while giveing rise to the study of interrelations between three main elements of the teaching process the: mathematical content to be taught and learned, management of the various time dimensions, and activity of the teacher who prepares and manages the class, to the benefit of the students' knowledge and the teachers' own experience. This volume, reprinted from Educational Studies in Mathematics, Volume 59, focuses on classroom situations as a unit of analysis, the work of the teacher, and is strongly anchored in original theoretical frameworks. The contributions are formulated from the perspective of one or more theoretical frameworks but they are tackled by means of empirical investigations.