Diagnostic errors have been termed the next frontier in patient safety, as these errors are quite common but have not yet been targeted outside of training programs. Diagnostic errors may be caused by individual or system-level problems, and this narrative review sought to develop a taxonomy of diagnostic error dimensions and identify approaches to addressing system-level causes. The authors identified five domains: provider–patient interaction (e.g., missing important symptoms); diagnostic testing (e.g., overuse or underuse of tests); follow-up (e.g., failure to act on abnormal test results); referrals (e.g., poor communication between providers); and patient-related issues. The investigators found that few of the interventions proposed to address these issues have been formally tested, leaving clinicians with little evidence to guide approaches to minimizing diagnostic error.