This volume offers a sampling of currently available instructional theories and describes the nature of the respective theories and features that may be important for anyone who wants to conduct research or use instructional theories in a practical situation. As in chapter 2 and elsewhere (e.g., Snelbecker, 1985), I use the term instructional theories instead of instructional-design theories and models. I prefer instructional theories because it is important to distinguish between the kinds of instruction that we are trying to design (reflecting instructional theories) and processes by which we design and develop instruction (especially reflecting design and development activities and views or theories). In Volume 1 (Snelbecker, 1983a), I suggested several groups of people who are somehow involved with instructional theory, and noted that they have divergent as well as common interests. I use the term knowledge producer to refer to theorists and researchers, and the term knowledge user to refer to instructional designers and instructors. I identify those groups again here as a reminder that we need to recognize ways in which people may differ in their expectations about and reactions to instructional theories.