Within the context of standards-based educational systems, states are using large scale reading assessments to help ensure that all children have the opportunity to learn essential knowledge and skills. The challenge for developers of accessible reading assessments is to develop assessments that measure only those student characteristics that are essential parts of the reading proficiency the test intends to measure, and not those characteristics that could be related to the student's disability. The National Accessible Reading Assessment Projects (NARAP) have been conducting research to identify ways to increase the accessibility of reading assessments. This document is the culmination of one of NARAP's goals: to develop evidence-based principles for making large scale assessments of reading proficiency more accessible for students who have disabilities that affect reading, while maintaining a high level of validity for all students taking the assessments. Some of the principles clarify and underscore the importance of well-accepted and widely used practices in designing reading assessments. Other principles have been developed from theory to respond to the needs of specific groups of students. Appendices include: (1) Support for Guidelines; (2) Principle 1; (3) Principle 2; (4) Principle 3; (5) Principle 4; and (6) Principle 5. (Contains 1 footnote.)