The recent National Academy of Medicine report on improving diagnosis cited the need for enhanced clinical decision support. This pre–post study used a simulation approach (standardized patients) to compare visits with and without use of a diagnostic clinical decision aid embedded in the electronic health record. The patients' visit satisfaction ratings did not differ in the visits with and without the decision support, although more patients in the decision support group noted that physicians focused more on the computer than the patient. The physicians reported high overall satisfaction with the decision tool, but they noted that it required inputting more clinical documentation during the visit, resulting in more time directed at the electronic health record. The authors conclude that the clinical decision support tool interface should be improved in order to facilitate adoption of real-time diagnostic support.