A theory of structure in teaching is presented and a system of analysis introduced which allows empirical investigation of verbal behavior in the classroom. Two kinds of structure are distinguished: "static" structure, defined as stable organized clusters of knowledge, and "kinetic" structure, defined as the sequential process of building up knowledge. Different organizational principles can be used to provide kinetic structure. It is argued on evolutionary and ontological grounds that spatial relatedness is the primary organizational principle, from which chronological and various symbolic organizational principles are derived. Classroom interaction is considered as a sequence of stimulus units (emitted by the teaching source) and response units (emitted by the student). Kinetic structure is considered to be highest when contiguous units have the greatest number of elements in common. A mathematical system for analyzing kinetic structure is outlined and examples of its application are given. Appendices include summaries of research based on this theory and a sample coded transcript of a biology lesson. (EB)