Instructional research is synthesized, using categories specific and functional enough to provide guidance for classroom practice. The opening chapter presents a theory for conducting a theory-based meta-analysis of the research on instruction, outlining a theory that involves four elements of human information processing: the self-system, the metacognitive system, the cognitive system, and knowledge. Chapter 2 describes the ways in which these four elements are represented in permanent memory. In chapter 3, the four elements and their subcomponents are described in detail. Chapter 4 describes specific design features of the meta-analysis, and chapters 5 through 8 present the results of the meta-analysis. Chapter 9 contains a general discussion of the findings in terms of classroom practice. In all, the meta-analysis used more than 4,000 effect sizes that involved an estimated 1,237,00 subjects. One observation that results from the meta-analysis is that the self-system appears to be the control center for human behavior, while the metacognitive system is the engine of learning. Three relatively straightforward implications are drawn. The teacher should: (1) identify knowledge and skills that are targets of instruction; (2) identify and use specific instructional techniques for specific instructional goals; and (3) use instructional techniques that apply to all types of instructional goals. (Contains 47 tables, 25 figures, and 398 references.) (SLD)