Intended to provide a knowledge base for intervention and remediation, this report summarizes what is currently known about patterns of children's reading and spelling substitution errors, with an emphasis on specific examples of the kinds of mistakes actually made by students. Following an introduction, preface, and preparatory quotes, the report is in nine sections: (1) Words: A Complex of Features; (2) Substitution Errors and Error Patterns; (3) Generalizations and Rules of Thumb; (4) The Assumption of Specificity; (5) Miscue Analysis and the Role of Context; (6) Developmental Spelling; (7) The Skill Based Approach; (8) Error Analysis Can Reveal Strengths; and (9) Conclusion. Forty-nine references are attached. (SR)