In this study we evaluated the usability of a widely used EHR interface that allow the entry of diagnostic terms, using multi-faceted methods to identify problems and work with the vendor to correct them using an iterative design method.Methods: Fieldwork was undertaken at two clinical sites, and dental providers as subjects participated in user testing (n=32), interviews (n=36) and observations (n=24).Results: User testing revealed that only 22–41{ca7ad0b74511a57bb2016f24c729dd7716d5352e92d2275aa1f91fb22c36b0a7} of users were able to successfully complete a simple task of entering one diagnosis, while no user was able to complete a more complex task. We identified and characterized 24 high-level usability problems reducing efficiency and causing user errors. Interface-related problems included unexpected approaches for displaying diagnosis, lack of v….