This monograph presents a diagnostic decision-making model for reading, elementary, and special education teachers to use as a guide in assessing and evaluating students' reading abilities to design and provide more appropriate reading instruction. The model in the monograph gives an overall perspective or gestalt of the components and strategies important to successful reading, and it provides a sequence for evaluating those components and strategies in a rational and efficient manner. The monograph is intended particularly for teachers who have adapted holistic, child-centered, or literature-based instructional rationales and who now assume responsibility for designing reading instruction for each student in their classes. Chapters in the monograph are: (1) Rationale and Purpose of the Diagnostic Decision-Making Model; (2) General Orientation to the Diagnostic Decision-Making Model; (3) The Diagnostic Process; and (4) A Complete Example: Sandra. Contains 66 references and 3 figures illustrating aspects of the model. (RS)