Instructional designers believe that it is important to expose pre-service and in-service teachers to Instructional Systems Design (ISD) procedures and products so teachers can utilize them. Educational literature, however, reveals few attempts to relate instructional design theory and methods to teaching practice. This paper proposes a new conceptual model for thinking about teaching that incorporates current findings of research on teachers' thinking and components of instructional design models and principles. The paper reviews the major findings of research on teacher thinking and instructional systems design, and then presents a conceptual model to bring the two closely related fields together. Potential implications of the model for instructional development and research in instructional design and teacher thinking include: (1) teachers and their teaching and learning processes can only be studied within their social and cultural context; (2) teachers' knowledge is a complex blend of personal, practical, and theoretical knowledge--research in teaching, learning, and instruction has to shift its emphasis from cognition to social construction of knowing; (3) the image of teachers as designers of their own instruction needs to be emphasized in the instructional technology field, and the instructional design models and principles should be reconceptualized if they are to be used by teachers; (4) the concept of design as an artistic, social, and cooperative act should replace the procedural and technical concept of design--instructional design activities should focus on the product of the design instead of the procedure; and (5) instructional design models and principles should focus on an approach in which the design objectives and strategies or solutions evolve as the teacher-designer becomes more acquainted with the social and cultural system and subsystems, and people who are affected by the design, including learners, should participate in the decision-making process. (Contains 84 references.) (SWC)