PROMIS (Patient-Reported Outcome Measurement Information System) is developing a set of tools for collecting patient reported outcomes, including computerized adaptive testing that can be administered using different modes, such as computers or phones. The user interfaces for these tools will be designed using the principles of universal design to ensure that it is accessible to all users, including those with disabilities. We review the rationale for making health assessment instruments accessible to users with disabilities, briefly review the standards and guidelines that exist to support developers in the creation of user interfaces with accessibility in mind, and describe the usability and accessibility testing PROMIS will conduct with content experts and users with and without disabilities. Finally, we discuss threats to validity and reliability presented by universal design principles. We argue that the social and practical benefits of interfaces designed to include a broad range of potential users, including those with disabilities, seem to outweigh the need for standardization. Suggestions for future research are also included.